---
name: game-design-vocabulary
description: Reverse-lookup glossary of 462 game design terms, from Verbs. Turns a vague description of a game idea into its exact term ("the jump still works after leaving a ledge" -> Coyote time; "the story says one thing, the game makes you do another" -> Ludonarrative dissonance), across mechanics, feel, challenge, level design, systems, psychology, story, worldbuilding, art, sound, interface, genres, multiplayer, technology, production and business. Use when someone describes a game idea or problem loosely and needs the right word, or when writing a game design brief.
---

# Game design vocabulary

When someone describes something in a game without its name, find the term below, say its name, and use it from then on. When a brief is vague, ask about it using these words.
Full entries with examples and playable toys: https://verbs.dqnotes.com/glossary.md

## What a game is

- **Verb** (Player action, What the player can do): What the player can do, named as a doing word: run, jump, shoot, trade, talk. The list of verbs is the quickest honest description of any game. Described as: "what the player actually gets to do", "the list of actions you can take", "what can I do in this game", "the things your character can do", "what does the button do".
- **Rule** (Game rule): A statement of what is allowed and what happens next: a bishop moves diagonally; touching a ghost costs a life. Rules stay the same however you play. Described as: "how the game decides what happens", "what you are and are not allowed to do", "the game stopped being fun when they changed one thing", "why can't I do that".
- **Goal** (Objective): What the player is trying to make happen. A goal turns every action into a good one or a bad one. Described as: "what am I supposed to be doing", "I don't know what I am trying to do", "what counts as doing well", "the point of the game".
- **Win and lose states** (End conditions, Game over, Fail state): The conditions that end the game, for better or worse: the flag is reached, the health runs out. Some games have one, both or neither. Described as: "can you lose this game", "you can't really die in this game", "the game has no ending", "what makes it game over", "endless mode".
- **Game state** (State, World state): Everything the game needs to remember at this moment: where each thing is, how fast it is going, whose turn it is, who is alive. All else can be rebuilt from it. Described as: "everything the game keeps track of", "what gets stored in a save", "after loading a save something was different", "the numbers behind what is on screen".
- **Mechanic** (Game mechanic): A verb together with the rules that answer it: what you do, and what the game does back. Double jump is a mechanic: the verb is jump, and the rule is that you may do it once more in the air. Described as: "the thing the game is built around", "how a feature works in the game", "the double jump, the grappling hook, that kind of thing", "the main gimmick of the game".
- **System** (Game system, Interlocking mechanics, Systemic design): A set of mechanics that feed into each other, so that what one does changes what another can do. Fire burns grass, grass grows back, and wind moves fire. Described as: "the game's parts all affect each other", "things happen that the designers did not plan", "one feature feeds into another", "emergent stuff", "you can solve it in ways they did not intend".
- **Core loop** (Gameplay loop, Compulsion loop): The short cycle of actions a player repeats the most, where finishing one round sets up the next. Fight, get loot, buy gear, fight something bigger. Described as: "the thing you keep doing over and over", "just one more turn", "what do you actually do minute to minute", "the cycle of the game", "it gets repetitive".
- **Feedback** (Player feedback, Game response): Any way the game tells you what just happened and how you did: a sound, a number, a flash, a word. It closes the gap between doing something and knowing what it did. Described as: "I can't tell if that worked", "did my hit even register", "the game doesn't tell me what I did wrong", "no idea why I lost", "it needs to show what happened".
- **Constraint** (Limitation, Design limit): A limit you put on the player on purpose: little ammo, one button, a clock, a small map. It takes away an easy answer so the player has to find a better one. Described as: "the game limits what you can do", "you only get a few bullets", "being forced to think because you can't do everything", "limited inventory on purpose".
- **Abstraction** (Simplification, Level of detail): Leaving out the parts of a real thing that do not matter to your game, and keeping the ones that do. A chess knight is a whole cavalry charge reduced to one L-shaped move. Described as: "the game simplifies something from real life", "it doesn't need to be that realistic", "just one number instead of all that detail", "how much detail to simulate".
- **Affordance** (Perceived affordance, Visual language): What an object lets you do, and how plainly it suggests that: a handle invites a pull, a ledge invites a climb. The psychologist James Gibson coined the word, and Don Norman brought it to design. Described as: "how do I know I can climb that", "the yellow paint on ledges", "I didn't know you could interact with that", "it looks like a door but it isn't", "things that show you how to use them".
- **Interesting decision** (Meier's rule, A series of interesting decisions): A choice with no obviously right answer, where you know enough to reason about it. A line credited to Sid Meier, from a 1989 talk, says a game is "a series of interesting decisions". Described as: "there is always one right answer", "the choice is obvious", "you have to weigh things up", "there are no real trade-offs", "I never have to think".
- **Meaningful choice** (Meaningful play, Real consequences): A choice whose result you can see and which changes what comes later. Katie Salen and Eric Zimmerman's Rules of Play asks for both: the outcome must be discernible and integrated into the larger game. Described as: "my choices don't matter", "it ends up the same whatever you pick", "the game remembers what you did", "your decisions have real consequences", "fake choices".
- **Progression** (Player progression, Gating, Unlocks): The way a game changes as you play, giving you more to do and more of it within reach: new abilities, new places, stronger numbers. Described as: "unlocking new stuff as you play", "the game keeps opening up", "I got an item and now I can go back", "levelling up", "why keep playing".
- **MDA framework** (Mechanics, dynamics, aesthetics, MDA): A way of seeing a game in three layers: mechanics are the rules, dynamics are what those rules do when played, and aesthetics are how it feels. It comes from a 2004 paper by Robin Hunicke, Marc LeBlanc and Robert Zubek. Described as: "why does changing one small rule change how the whole game feels", "what kind of fun is this", "designers see rules, players see feelings", "what does fun actually mean".
- **Magic circle** (The circle of play): The boundary between a game and ordinary life. Inside, rules and goals you would never accept elsewhere are real. Johan Huizinga used the phrase in Homo Ludens (1938), and Rules of Play made it a term of game design. Described as: "it's only a game", "things that are fine in a game but not in real life", "something broke the spell", "being a jerk in a game versus being one for real".
- **Lusory attitude** (Accepting the rules): Agreeing to a game's rules because they make the game possible, though there are easier ways to reach the goal. Bernard Suits defined playing a game as "the voluntary attempt to overcome unnecessary obstacles". Described as: "why do people play by rules they could ignore", "I could just cheat but that wouldn't be fun", "making a game harder on purpose", "self-imposed challenge runs", "you could just pick the ball up".
- **Paidia and ludus** (Free play and structured play, Play and game): Two ends of one scale, named by Roger Caillois. Paidia is free, made-up play, with no rules to speak of. Ludus is play bound by rules and goals, made harder on purpose. Described as: "just messing around in the game", "playing without trying to win", "sandbox versus structured", "making up your own games inside the game".
- **Four kinds of play** (Agon, alea, mimicry, ilinx, Caillois's categories): Roger Caillois's four appeals of play, from Man, Play and Games (1958): agon is contest, alea is chance, mimicry is make-believe, and ilinx is vertigo. Most games mix several. Described as: "competition, luck, pretending and dizziness", "different kinds of fun", "why do people like gambling games", "the rush of going really fast", "playing pretend".
- **Toy versus game** (Software toy, Sandbox): A toy is something fun to handle with no goal attached. A game adds a goal and some way of failing at it. Many good games are a good toy with a game built around it. Described as: "it's fun just to mess around with", "there is nothing to actually do but I keep playing", "a sandbox with no objective", "is this even a game".
- **Player fantasy** (Power fantasy, Class fantasy, Role fantasy): Who the game lets you feel you are: a dragon, a master thief, someone who gave up a desk job to run a farm. It is a promise that the numbers, the verbs and the art all have to keep. Described as: "the game makes you feel like a badass", "I want to feel like a real wizard", "it doesn't feel like being a dragon", "who am I in this game", "living out being a farmer".
- **Design pillars** (Pillars, Core pillars): A short list, usually three to five words or phrases, stating what a game must be. Every feature is checked against them, and whatever does not serve one gets cut. Described as: "what is this game really about", "how do we decide what to cut", "too many features", "scope creep", "the core ideas everything has to fit".

## Feel

- **Game feel** (Feel, Kinesthetics): The physical sensation of controlling something in a game: how directly it answers you, how much it seems to weigh, how its impacts land. Steve Swink named its parts in his 2008 book Game Feel. Described as: "the game just feels good to move around in", "controls feel nice and responsive", "why does this jump feel bad", "the movement feels floaty or heavy".
- **Acceleration** (Ramp-up, Tight controls (when short)): The time a character takes to go from standing to top speed, and its partner deceleration, the time to stop again. Short feels tight. Long feels heavy or slippery. Described as: "the character takes too long to start moving", "the character slides when you let go", "it feels like walking on ice", "tight controls".
- **Coyote time** (Ledge forgiveness, Late jump): The short moment after running off a ledge when a jump still works. It is named after Wile E. Coyote, who hangs in the air until he looks down. Described as: "you can still jump right after running off a ledge", "the game lets me jump after I have already left the platform", "jump works in mid-air for a moment", "I pressed jump and fell anyway".
- **Jump buffering** (Input buffer, Early jump): The game remembers a jump pressed just before landing and performs it on the first frame you touch the ground. Described as: "I pressed jump just before landing and nothing happened", "the game remembers my button press", "jumping right as you land", "the button sometimes ignores me".
- **Variable jump height** (Jump cut, Hold to jump higher): A tap makes a short hop, a hold makes a full jump. In practice, letting go early just increases gravity for the rest of the rise. Described as: "tap for a small hop, hold for a big jump", "holding the button makes you jump higher", "short hop", "letting go early cuts the jump short".
- **Fast fall** (Fall gravity, Asymmetric gravity): Stronger gravity on the way down than on the way up. A real thrown ball has an even arc; a good video game jump usually does not. Described as: "the jump feels floaty", "falling should be faster than rising", "the character hangs in the air too long", "give the jump more weight".
- **Apex hang** (Hang time, Jump peak gravity): Gravity eases for a moment at the top of a jump, so the character hangs there briefly. It buys time to aim the landing. Described as: "the character hangs at the top of the jump", "a floaty moment at the peak", "more time to aim the landing".
- **Air control** (Aerial steering): How much you can change direction while in the air. Physics says none. Most games give nearly all of it. Described as: "you can steer while jumping", "you can change direction in the air", "once you jump you are committed".
- **Corner correction** (Corner nudge, Ledge snap): When your head clips the very corner of a block during a jump, the game slides you sideways around it rather than stopping you dead. Described as: "the game nudges you around a corner", "bumping your head on a corner stops the jump", "the jump got caught on the edge of a block".
- **Squash and stretch**: A shape flattens on impact and pulls long at speed, and keeps its volume while doing it. It is the first of Disney's twelve principles of animation. Described as: "the character squishes when it lands", "it goes flat on impact and stretches when it jumps", "rubbery bouncy animation", "give it more weight when it lands".
- **Anticipation** (Wind-up, Telegraph (on enemies)): A small movement the other way before a big one: a crouch before a jump, a pulled-back arm before a punch. Another of Disney's twelve principles. Described as: "the wind-up before a big move", "crouching before a jump", "the pull-back before a hit", "you can see the attack coming".
- **Follow-through** (Overlapping action, Secondary motion): Loose parts keep moving after the main body stops: hair, capes, a tail, a scarf. They arrive late and settle slowly. Described as: "the cape keeps moving after the character stops", "hair and clothes drag behind", "floppy parts trailing behind", "wobbly bits that catch up".
- **Particles** (Particle effects, VFX, Dust and sparks): Many small, short-lived sprites thrown off by an event, each with its own speed, fade and gravity: dust on a landing, sparks on a hit. Described as: "dust when you land", "sparks flying when you hit something", "little bits that fly off", "effects when things collide".
- **Hit stop** (Hit pause, Hitlag, Freeze frames): The game freezes for a few frames at the moment of impact. Fighting games have used it for decades, and it is among the strongest tools for making a blow feel heavy. Described as: "the game freezes for a split second when you hit something", "hits feel crunchy and heavy", "attacks have no impact", "a tiny pause on impact".
- **Screen shake** (Camera shake, Trauma): The camera jolts when something big happens. Good shake is driven by a "trauma" value that decays, with the offset following trauma squared, so small hits stay small. Described as: "the screen shakes when something explodes", "the camera jolts on impact", "make explosions feel big".
- **Juice** (Game juice, Polish, Game feel effects): All the extra feedback that makes a small action feel big: sound, particles, shake, flashes, bounce. The term spread through the 2012 talk Juice It or Lose It by Martin Jonasson and Petri Purho. Described as: "making the game feel more satisfying", "it works but it feels flat", "adding polish and feedback to everything", "pop and sparkle when you do things".
- **Camera lookahead** (Camera lead, Forward focus): The camera leans toward where you are heading, so you see more of what is coming than what you have passed. Described as: "the camera shows more of what is ahead", "I cannot see what is coming", "the view moves ahead of the character".
- **Camera dead zone** (Camera window, Camera trap): A box around the middle of the screen in which the player can move without the camera moving at all. The camera only follows once they push against the edge of the box. Described as: "the camera does not move until you reach the edge of a box", "small movements should not move the screen", "the camera feels jittery".
- **Platform snapping** (Vertical camera lock, Ground anchoring): The camera follows up and down only when the player lands on something, not during every jump. Described as: "the camera bounces every time you jump", "the camera stays still during a jump", "the screen moves up and down too much".
- **Input latency** (Input lag, Button-to-pixel delay): The time between pressing a button and seeing the result on screen. Every stage adds some: the controller, the game's frames, the display. Described as: "the controls feel laggy", "there is a delay between pressing and seeing", "the game feels sluggish to respond", "input lag".
- **Frame rate** (FPS, Frames per second): How many new pictures the game shows each second. Higher looks smoother and also shortens the delay before your press can show up. Described as: "the game looks choppy", "the game stutters", "smoother animation", "30 versus 60".
- **Hitbox** (Hurtbox, Collision box): The invisible shape the game actually checks for contact. Strictly, a hitbox deals damage and a hurtbox receives it. Neither has to match the art. Described as: "it did not even touch me", "the invisible shape that detects hits", "what counts as getting hit", "I got hit from far away".
- **Invincibility frames** (I-frames, Mercy invincibility): A brief window in which you cannot be hurt. After taking damage it stops one mistake killing you twice. On a dodge, it is what makes rolling through an attack possible. Described as: "the character flashes after getting hit", "you cannot get hurt for a moment", "rolling through attacks", "dodging through an attack".
- **Frame data** (Startup, active, recovery): Any attack can be measured in three stretches: startup before it can hit, active frames when it can, and recovery before you can act again. Described as: "how long an attack takes to come out", "the wind-up and cooldown of a move", "how long until I can act again after attacking".
- **Animation cancelling** (Cancel, Interrupt): Cutting one action short by starting another, skipping its recovery. Some games forbid it, some allow it, some build everything around it. Described as: "interrupting an attack with another move", "skipping the end of an animation", "locked in the animation and cannot dodge".
- **Aim assist** (Magnetism, Reticle friction, Auto-aim): The game quietly helps you aim. Usually friction, where the cursor slows near a target, and magnetism, where it pulls gently towards one. Described as: "the crosshair sticks to enemies", "the game helps you aim", "aiming with a controller feels hard".
- **Stick dead zone** (Analogue dead zone): A small circle in the middle of a thumbstick's range where movement is ignored, so that worn sticks that do not centre perfectly do not make your character creep. Described as: "my character moves by itself", "controller drift", "the stick does nothing for small movements".
- **Haptics** (Rumble, Vibration, Force feedback): Feedback you feel through the controller: from one spinning motor to precise actuators that can suggest texture and resistance. Described as: "the controller vibrates", "feeling the game in my hands", "rumble when something hits".

## Challenge

- **Difficulty curve** (Challenge curve, Ramp): How hard a game is over time, drawn as a line. A good one starts low and climbs at about the speed the player is getting better. Described as: "the game gets harder too fast", "how hard the game gets over time", "it starts easy and ramps up", "the game never gets any harder", "when it should get harder".
- **Difficulty spike** (Difficulty wall, Brick wall): One point where a game suddenly gets much harder than what came before, and then often eases off again. Described as: "the game was fine and then suddenly impossible", "everyone gets stuck at this one bit", "I hit a wall", "where everybody quits the game".
- **Learning curve** (Skill curve, Onboarding slope): How quickly a player gets better at a game with practice. People say "steep" to mean hard to learn, though on a real chart a steep curve means learning fast. Described as: "the game is hard to get into", "it takes ages to understand", "easy to learn hard to master", "too much to take in at the start", "how long until I get good".
- **Skill floor and ceiling** (Low floor, high ceiling, Easy to learn, hard to master): The floor is the least skill you need to do anything at all. The ceiling is the most skill the game can reward. The two can be moved separately. Described as: "anyone can pick it up but pros are on another level", "too hard for beginners", "nothing left to master", "experts have nothing to do", "easy to learn hard to master".
- **Teach, test, twist** (Kishōtenketsu in levels, Introduce, develop, twist): A way of building a level around one idea: show it somewhere safe, ask for it where failure counts, then change it so that what you learned has to bend. Then move on. Described as: "the level teaches you without telling you", "first it shows you safely, then it gets dangerous", "how Mario levels introduce things", "I learned it without a tutorial".
- **Pacing** (Rhythm of play, Beats): The order and length of what you ask of the player: fight, rest, explore, talk, fight again. It is about what comes after what, more than how hard any one part is. Described as: "the game never lets up", "it drags in the middle", "too much walking between the good bits", "there is no time to breathe", "one fight after another".
- **Sawtooth pacing** (Sawtooth difficulty curve, Peaks and valleys): Difficulty that climbs, drops, then climbs higher, like the teeth of a saw. Each hard stretch ends with an easy one, and the overall trend keeps rising. Described as: "the difficulty goes up and down", "an easy level after a hard one", "it gives you a break after a tough section", "getting harder overall with breathers".
- **Intensity curve** (Drama curve, Encounter pacing): How intense the action feels from moment to moment, drawn as a line. Designers shape it with peaks and valleys, and some games measure it live and react. Described as: "the game knows when to back off", "quiet moments between the big fights", "the action comes in waves", "it feels like the same intensity all the time".
- **Tension and release** (Build and release, Relief): Letting worry build, then letting it go. A long held threat followed by safety hits harder than either alone, and the relief is often what players remember the most. Described as: "the relief of finding a safe room", "a horror game stops being scary", "it builds up and then you can breathe", "being scared the whole time gets boring".
- **Telegraphing** (Tell, Wind-up, Attack cue): Showing what is about to happen before it does, in time for the player to respond: a raised arm, a glow, a sound. It turns an attack into a question the player can answer. Described as: "you can see the attack coming", "the boss winds up before it hits", "it hit me out of nowhere", "no warning before the attack", "learning the enemy's moves".
- **Fair failure** (Fair death, Earned failure): Failing in a way the player accepts as their own doing: they saw it coming, they know what went wrong, and they know what to try next. Whether a death feels fair matters more than how often it happens. Described as: "that death was cheap", "I died and I don't know why", "it feels unfair", "hard but fair", "it was my fault and I want another go".
- **Cost of failure** (Death penalty, Failure state cost, Setback): What you lose when you fail: seconds, progress, items, or the whole run. It is a separate dial from how hard the game is. Described as: "I have to do all that again", "what do I lose when I die", "checkpoints too far apart", "instant respawn", "dying sets you back too much".
- **Permadeath** (Permanent death, Hardcore mode, Ironman): When a character dies, they are gone for good, with no reloading. It may end the whole run or only remove that one character. Described as: "if you die you start all over", "you can't reload", "losing a character forever", "one life", "hardcore mode".
- **Risk and reward** (Push your luck, Risk-reward): Giving the player a safe option and a dangerous one that pays better. The risk has to be real and the reward has to be worth it. Described as: "do I go for it or play it safe", "one more and I might lose everything", "the dangerous route pays better", "should I bank what I have", "there is no reason to take the risk".
- **Time pressure** (Timer, Countdown, Clock): Limiting how long a player has to act. It changes the kind of thinking a task takes, from careful working out to quick judgement. Described as: "the timer makes me panic", "hurry up music", "you have to decide fast", "I can't think with the clock running", "a countdown makes it exciting".
- **Execution versus knowledge** (Skill versus knowledge, Dexterity versus puzzle): Two kinds of challenge. Execution is about being able to do it: timing, precision, nerve. Knowledge is about knowing what to do: the trick, the route, the answer. Described as: "once you know the trick it's easy", "I know what to do but I can't do it", "looking it up ruins it", "puzzle versus reflexes", "practice versus figuring it out".
- **Skill gate** (Skill check, Gatekeeper): A deliberate point you cannot pass until you can do a certain thing. It stops you moving ahead without a skill that everything later will demand. Described as: "I can't progress until I learn this", "the boss that forces you to use the new move", "you have to learn the mechanic to pass", "the game finally made me learn to parry".
- **Boss** (Boss fight, End-of-level boss): A big set-piece enemy that ends a stretch of the game and tests what the stretch taught you. Usually it has phases: as its health falls, it changes how it fights. Described as: "the big enemy at the end of the level", "it changes attacks when its health gets low", "a bullet sponge", "health bar at the top of the screen".
- **Difficulty modes** (Difficulty settings, Easy, normal, hard): Versions of the same game tuned for different players, chosen by the player, usually at the start. They change numbers such as enemy health, damage and how many enemies there are. Described as: "easy normal hard", "choosing how hard the game is at the start", "I picked hard and regretted it", "the easy mode makes fun of you".
- **Assist mode** (Assist options, Accessibility settings): A menu of separate settings that make specific things easier, each your own choice: slower game speed, extra jumps, no damage. You keep the rest of the game as it was designed. Described as: "slow the game down so I can play it", "I can't do this for physical reasons", "can I turn off dying", "options that help without changing the game", "an easy mode without the shame".
- **Invisible assistance** (Hidden mechanics, Player-favouring tricks, Generous design): Help the game gives you without saying so: a hit area smaller than it looks, a health bar that drains more slowly near the end, a jump that works just after the ledge. Described as: "I survived with one pixel of health", "the game is secretly helping me", "that should have hit me", "always just barely making it", "the game lets you off".
- **Dynamic difficulty adjustment** (DDA, Adaptive difficulty): The game watches how you are doing and changes its difficulty while you play, usually without telling you. Do badly and it eases off; do well and it pushes harder. Described as: "the game gets easier when I keep dying", "the game adapts to how good you are", "it noticed I was struggling", "it got harder because I was doing well".
- **Rubber-banding** (Rubber band AI, Catch-up mechanic): Pulling competitors back together: those in front are held back and those behind are helped along, as if everyone were joined by elastic. Described as: "the computer always catches up to me", "you can never get a real lead", "blue shell", "the racers are glued to you", "being in last gives you better items".
- **Grinding** (Farming, Level grinding): Repeating easy tasks, not for their own sake, but to build up the experience or items that let you progress. The player has mastered the task and is just waiting for a number. Described as: "I have to fight the same monster for hours", "killing time to level up", "the game makes you repeat things to progress", "farming for gold", "it feels like a job".
- **Mastery** (Skill mastery, Competence): Getting really good at something, and being able to see that you have. The challenge stays still and you are the one who changes. Described as: "I got so much better at this game", "beating my own time", "finally being good at it", "years later and still improving", "getting good".

## Space

- **Critical path** (Golden path, Main path): The shortest route through a level or game that still gets you to the end, touching only what is required. The golden path is its richer cousin: the route designers hope most players take, past the things worth seeing. Described as: "the shortest way to finish the game", "the main route through a level", "the bare minimum you need to do to beat it", "the way the designers want you to go", "what every player definitely sees".
- **Landmark** (Orientation point, Navigational landmark): Something big and unique that can be seen from far away, so players always know where they are relative to it. Lost people navigate by these in cities, and players do the same. Described as: "I keep getting lost in this level", "all the streets look the same", "a tall thing you can see from everywhere", "something to get your bearings from".
- **Weenie** (Wienie, Visual magnet): A big, tempting sight placed at the end of a route, so people walk towards it without being told. Walt Disney's term: Sleeping Beauty Castle at the end of Main Street is the first and most famous one. Described as: "the thing in the distance makes you want to go there", "something big drawing you towards it", "the castle at the end of the street", "leading players with a view instead of a marker".
- **Breadcrumbing** (Breadcrumbs, Breadcrumb trail): A trail of small rewards or items, each in sight of the last, that leads the player along a route. The player only ever decides to get the next one. Described as: "a trail of coins showing where to go", "following a line of pickups", "little rewards that lead you along", "collectibles pointing the way".
- **Signposting** (Yellow paint, Visual language, Affordance marking): Marking what matters so that it stands out from everything else: a colour on every climbable ledge, a light over the correct door, one kind of crack on every wall that breaks. Players learn the code once and read it for the rest of the game. Described as: "the yellow paint on things you can climb", "how do I know which ledge to grab", "I walked past the door because it looked like the others", "making the right way stand out", "the game marks what you can interact with".
- **Funnelling** (Funneling, Player flow, Soft guidance): Shaping a space so that people drift towards one place without noticing: walls that lean inward, a road that narrows, a floor that slopes down. They believe they chose the route. Described as: "the level gently pushes you the right way", "walls that lead you to the exit", "players keep wandering around the room looking for the way out", "guiding people without telling them".
- **Gating** (Progression gate, Hard gate, Soft gate): Anything that stops the player going further until they have done something. A hard gate cannot be passed at all. A soft gate can be, but it is dangerous or expensive to try early. Described as: "you can't go there until you have the ability", "the game blocks you until you do something", "the area you can see but can't reach yet", "something stopping you from skipping ahead".
- **Lock and key** (Key and door, Ability gate): A gate that one specific thing opens. The key may be an actual key, or an ability that works as one: a hookshot, a double jump, a bomb. Described as: "find the red key to open the red door", "you need an item to get through", "a door you can only open later", "getting a new ability opens up new areas".
- **Soft lock** (Softlock, Unwinnable state, Dead end): The game is still running and you can still move, but you can no longer finish it, and it does not tell you. A hard lock is the frozen version, where nothing responds at all. Described as: "I'm stuck and there's no way to continue", "the game didn't tell me I could no longer win", "I used my last key on the wrong door", "I have to reload because I can't get back up there", "the game is still running but nothing can be done".
- **Teaching through level design** (Show, don't tell, Silent tutorial, World 1-1): Arranging the first spaces so that the player works out the rules by bumping into them, safely, with no text. The obstacle comes first, in a place where failing costs nothing, and the lesson arrives as an idea of their own. Described as: "the game teaches you without telling you", "no tutorial but you still figure it out", "the first level shows you how to play", "a safe place to try the jump before it matters", "learning by doing".
- **Kishotenketsu** (Kishōtenketsu, Four-step level design, Ki-sho-ten-ketsu): A four-part structure from Chinese poetry and Japanese four-panel comics: introduce an idea, develop it, twist it, conclude. There is no conflict required. In a level, one mechanic gets those four beats and then the level ends. Described as: "the level introduces an idea then twists it", "each Mario level has one idea and then it ends", "four-part structure for a level", "a level that surprises you with its own mechanic".
- **Player metrics** (Metrics, Character metrics, Level metrics): The measurements of what the character can do: jump height, longest jump, run speed, how high a wall they can climb, how wide a door they fit through. Every level is built out of these numbers. Described as: "how far can the character jump", "the gaps in my level don't work any more", "I changed the run speed and broke all the levels", "how wide should a door be", "measurements for building levels".
- **Sightline** (Line of sight, LOS, Sight lane): How far and where a player can see, and be seen, from a given spot. In a shooter, a sightline is also a line of fire: if I can see you, I can hit you. Described as: "how far you can see from here", "someone sniped me from the other side of the map", "that spot can see the whole map", "I got shot from somewhere I couldn't see".
- **Choke point** (Chokepoint, Bottleneck): A narrow place every attacker must pass through, so only a few of them can fight at once. Numbers stop counting: the side in the narrow place fights the front rank, not the army. Described as: "everyone has to go through one narrow door", "a few defenders can hold off a whole team", "the map bottlenecks here", "a narrow pass where the fight happens".
- **Cover** (Hard cover, Half cover, Cover system): Anything that stops bullets and that you can stand behind. Its height and spacing decide the rhythm of a fight: pop out, shoot, get back, move to the next piece. Described as: "hiding behind walls so you don't get shot", "crouching behind a crate", "there's nowhere to hide in this room", "popping out to shoot and ducking back".
- **Flanking route** (Flank, Side route, Third lane): A second way into a fight that comes at the enemy from the side or behind. It exists so that a defender can never watch everything at once. Described as: "coming at them from the side", "getting behind the enemy", "there's only one way in and it's a stalemate", "I got shot in the back".
- **Verticality** (High ground, Vertical level design): Using height as part of the layout, so that where you stand up and down matters as much as where you stand across. Whoever is above sees more and has less exposed to them. Described as: "getting up high to see more", "the high ground wins", "the level feels flat", "attacking from above", "climbing up to get an advantage".
- **Arena** (Combat space, Kill box, Lock-in): A space built for one fight: big enough to move around in, usually with exits closed until it ends. The room itself sets the terms, so you can't solve it by backing into the last corridor. Described as: "the doors lock until you kill everything", "a big room built for a fight", "players keep retreating to a doorway and shooting from there", "you have to keep moving in this fight".
- **Encounter design** (Combat encounter, Enemy mix, Wave design): Choosing which enemies, how many, where they start and when they arrive, for one fight in one space. The same six enemies can be trivial or terrifying depending on the mix. Described as: "which enemies to put in a fight", "every fight feels the same", "mixing enemy types so you have to change tactics", "planning a battle room by room", "waves of enemies".
- **Backtracking** (Retreading, Going back the way you came): Sending the player back through a place they have already been. Done well, the place has changed or they have: new powers open new doors. Done badly, it is the same corridor again with nothing to do. Described as: "making me walk all the way back", "going through the same area again", "coming back later with a new ability", "the game reuses the same rooms".
- **Shortcut** (Looping level design, Loop back, One-way door): A door, lift or ladder that links a far part of the level back to an earlier one, usually opened from the far side. Looping level design builds the whole map around these, so the level folds back on itself. Described as: "a door that opens back to the start", "the level loops back on itself", "I had to walk all the way back after dying", "unlocking a quicker way through", "the elevator back to the start".
- **Hub and spoke** (Hub world, Hub level, Overworld hub): A central place with levels or regions branching off it, so that the player returns to the middle and picks where to go next. Described as: "a central area with levels coming off it", "if I'm stuck on one level I can try another", "choosing which level to do next", "a home base you keep coming back to".
- **Density** (Negative space, Content density, Breathing room): How much there is to do in a given stretch of ground, and how much empty ground lies between. The emptiness is negative space, and like the gap between notes in music, it is doing a job. Described as: "there's too much stuff on the map", "the world feels empty", "walking for ages with nothing to do", "quiet moments between the action", "so many icons I stopped caring".
- **Set piece** (Setpiece, Scripted sequence, Spectacle moment): A big, expensive moment built once for one place, often scripted, that the player will talk about afterwards: the building that falls down while you are in it. Described as: "a huge scripted moment", "the bit everyone talks about after playing", "the building collapses while you're running through it", "a one-off spectacle level".
- **Vista** (Reveal, Overlook, Compression and release): A wide view placed deliberately, usually after a tight space, so the world seems to open up all at once. Tunnels and cave mouths do half of the work, because the eye has just been starved of distance. Described as: "coming out of a tunnel and seeing the whole world", "a beautiful view you stop to look at", "the moment the level opens up", "walking out of the cave at the start".
- **Secrets** (Hidden areas, Secret rooms, Easter eggs (when they are a joke)): Things placed off the main route for people who look for them: a wall that is not a wall, a ledge you must think to jump to. Their value is in being found, which needs a hint fair enough to notice. Described as: "a hidden room behind a fake wall", "rewards for exploring off the path", "the game counts how many secrets you found", "going off the main route and finding something".

## Systems

- **Resource** (Currency, Economy): Anything a player has a limited amount of and can spend or use up to get something else: gold, ammunition, health, time on the clock, a turn. If it is scarce and you can choose how to spend it, it is a resource. Described as: "the things you collect and spend", "gold and mana and ammo", "something you run out of", "having to choose what to spend it on".
- **Positive feedback loop** (Snowballing, Rich get richer, Reinforcing loop): A loop where doing well makes you better at doing well: winning gets you the thing that helps you win. Positive here means it amplifies, not that it is good. Described as: "the rich get richer", "once you're ahead you can't lose", "the game snowballs", "the first fight decides everything", "winning makes you win more".
- **Negative feedback loop** (Rubber banding, Catch-up mechanic, Balancing loop): A loop that pulls the leader back or lifts whoever is behind, so that the contest stays close. Negative here means it dampens, not that it is bad. Described as: "the game helps whoever is losing", "rubber banding in racing games", "blue shell", "the leader keeps getting punished", "catch-up mechanics".
- **Emergence** (Emergent gameplay, Emergent behaviour): Behaviour that nobody wrote, arising from a few simple rules interacting. The game's designers can be as surprised by it as anyone. Described as: "players found a strategy the designers never planned", "simple rules creating complicated results", "the game does things nobody programmed", "unscripted moments", "something unexpected came out of the rules".
- **Systemic design** (Chemistry engine, Multiplicative gameplay, Immersive sim logic): Building a game from general rules that apply to everything, rather than special cases for each puzzle. If fire burns grass, it burns all grass, whoever lit it, and any solution those rules allow is a real solution. Described as: "everything in the game follows the same rules", "if it should work, it works", "you can solve puzzles in ways they didn't plan", "set the grass on fire to kill the enemies", "rules that interact with each other".
- **Faucets and sinks** (Sources and drains, Gold sink, Money sink): A faucet creates a resource out of nothing, as when monsters drop gold. A sink destroys it for good, as when you pay an NPC for repairs. Money passing between players is neither: it just moves. Described as: "where does all the gold come from", "everyone has too much money", "something to spend money on to remove it", "gold sink", "money just keeps piling up".
- **Inflation** (Mudflation, Runaway prices, Hyperinflation): Prices rise because there is more money around, not because anything got better. In a game with no sinks it is almost guaranteed, since players keep producing money and rarely destroy it. Described as: "prices keep going up", "new players can't afford anything", "gold is worthless", "players trade items instead of money", "the economy is broken".
- **RNG** (Random number generator, PRNG, Luck): The part of a game that makes up random numbers. It is really a formula that produces a long list that only looks random, starting from one number called a seed, so the same seed always gives the same list. Described as: "random number generator", "the game is just luck", "reloading gives the same result", "how does the game decide random things", "same seed gives the same world".
- **Input and output randomness** (Pre-roll and post-roll, Input luck, Output luck): Input randomness happens before you choose, and you plan around it: the cards you were dealt, a random map. Output randomness happens after you choose and can overturn it: you aim, and then a die says whether you hit. Described as: "I had a 95% chance and missed", "the dice ruined my plan", "random but you can plan around it", "losing feels unfair because of luck", "good luck or good play".
- **Pseudo-random distribution** (PRD, Bad luck protection, Shuffle bag): Randomness that bends towards its average: each miss raises the chance of the next hit, and each hit resets it. The long-run rate stays the same and the streaks mostly go away. A shuffle bag does a similar job by dealing out a fixed set. Described as: "the game must be rigged", "I missed ten times in a row at 50%", "random feels too streaky", "the game secretly evens out luck", "bad luck protection".
- **Pity timer** (Pity system, Hard pity, Soft pity, Bad luck protection): A guarantee that after so many failed rolls, the next one pays out. It cuts off the worst luck anyone can have, without changing the rate for everyone else very much. Described as: "guaranteed drop after a number of tries", "I have been unlucky for so long", "the game takes pity on you", "counting pulls until the guarantee", "how many rolls until I get it".
- **Weighted loot table** (Loot table, Drop table, Drop rates): A list of what can drop, each with a weight. Add up the weights, roll a number in that range, and see whose slice it lands in. A weight of 1 in a table totalling 100 is a 1% chance. Described as: "how often does this item drop", "rare items and drop rates", "what's the chance of getting a legendary", "the list of what an enemy can drop".
- **Opportunity cost** (Trade-off, Tempo cost, What you gave up): What a choice really costs you is the best other thing you could have done with it. The gold you spent on a farm is a soldier you don't have when the raid comes. Described as: "if I buy this I can't buy that", "should I save or spend", "greedy early or safe", "every choice has a trade-off", "you can't have both".
- **Dominant strategy** (Optimal strategy, No-brainer, Solved): A choice that is at least as good as every alternative, whatever the opponent does. Once people find it, the rest of your options might as well not exist. Described as: "one option is just the best", "everyone uses the same weapon", "there's no reason to pick anything else", "the game is solved", "the only way to play".
- **Intransitive balance** (Rock paper scissors, Counter system, Weapon triangle): A loop of counters where A beats B, B beats C and C beats A, so there is no best choice, only a best choice against what the other side is doing. Described as: "rock paper scissors", "everything has a counter", "there's no best unit", "weapon triangle", "type advantages".
- **Power curve** (Linear growth, Exponential growth, Progression curve, Scaling): How a player's strength rises over time, usually drawn against the same for enemies. Linear growth adds the same amount each step. Exponential growth multiplies by the same amount each step, so it starts slowly and then leaves everything behind. Described as: "numbers get huge late in the game", "the game gets too easy after a while", "enemies scale with you", "how fast should the player get stronger", "exponential growth in idle games".
- **Soft cap and hard cap** (Diminishing returns, Stat cap, Level cap): A hard cap is a limit that can't be passed. A soft cap is a point past which each extra bit does less, so more is still allowed, and hardly worth buying. Described as: "putting more points in does almost nothing", "there's a maximum you can reach", "diminishing returns", "this stat stops working after a point", "is it worth putting more into this".
- **Buff and nerf** (Balance patch, Rework): A buff makes something stronger and a nerf makes it weaker. Nerf is named after the foam toys: a nerfed weapon is one that now hits like foam. Described as: "they made my favourite weapon weaker", "balance patch", "this character needs to be stronger", "why does a tiny change make such a big difference".
- **The meta** (Metagame, Tier list, Flavour of the month): What most people are playing at the moment, and the choices that makes best in reply. It is the game above the game: you don't only pick what's strong, you pick what beats what everyone else is picking. Described as: "everyone is using the same build", "what's strong right now", "tier lists", "copying the best players' setup", "the popular strategy changes over time".
- **Tech tree** (Skill tree, Research tree, Talent tree): A map of upgrades where each one requires those before it, so that buying one opens the next. You can't afford all of it, so your path through it is your strategy, and it is visible to you and often to your rivals. Described as: "research this to unlock that", "skill tree", "upgrades that lead to better upgrades", "choosing which branch to go down", "I wish I could get all the skills".
- **Build diversity** (Build variety, Viable builds, Option space): How many different ways of setting up your character or army are actually good enough to use. A game may offer thousands, and only the ones close to the best count. Described as: "every top player uses the same setup", "there are lots of items but only one good build", "how many builds are actually viable", "you have to take this item".
- **Min-maxing** (Dump stat, Optimising, Theorycrafting): Making one thing as high as you can by making another as low as you dare. Which build is best follows from the formula, so changing the formula changes how people play. Described as: "putting every point in one stat", "making your character as strong as possible by ignoring everything else", "the optimal build", "dump stat", "squeezing out the best numbers".
- **Action economy** (Actions per turn, Tempo): In a turn-based fight, how many things each side gets to do. A party of four with four actions usually beats one monster with four times the health and damage, because that single monster wastes damage and can be stunned out of its whole turn. Described as: "the boss dies too fast against a full party", "the side with more turns always wins", "one big enemy loses to four small ones", "stun is too strong", "bonus actions".
- **DPS and time to kill** (TTK, Damage per second, Breakpoint): DPS is average damage over time. Time to kill is how long it really takes to bring something down. They differ because damage comes in lumps: it takes a whole extra shot to deal the last point of damage. Described as: "how fast does this weapon kill", "I die before I can react", "damage per second", "this gun takes one less shot", "how many hits to kill".
- **Perfect imbalance** (Rotating meta, Controlled imbalance): Keeping a competitive game a little off balance on purpose, and changing which way it leans every so often. Players never settle on one solved answer, so there is always something new to work out. Extra Credits popularised the phrase in 2012. Described as: "the balance keeps changing every patch", "the game is never fully figured out", "they keep shaking things up", "slightly unbalanced on purpose".
- **Nash equilibrium** (Game theory optimal, GTO, Mixed strategy): A set of strategies where nobody can do better by changing theirs alone. Often it means mixing your choices in exact proportions, so that the other side can't exploit you whatever they do. Described as: "nobody can do better by changing what they do", "if I always do the same thing they exploit me", "the mathematically correct way to play", "mixing it up so I can't be read", "game theory optimal".
- **Prisoner's dilemma** (Iterated prisoner's dilemma, Tit for tat, Cooperate or defect): Two players each pick cooperate or betray. Betraying is always better for you whatever the other does, yet both end up worse off than if both had cooperated. Play it many times and things change, because betrayal can then be punished. Described as: "why does everyone betray each other", "we'd both be better off working together", "split or steal", "cooperate or backstab", "players turn on each other for loot".

## The player's mind

- **Intrinsic motivation** (Playing for its own sake, Internal motivation): Doing something because the doing is the reward. Nobody plays tag for the points. Described as: "I would play this even with no rewards", "it is fun for its own sake", "playing just because you like playing", "nobody is making me do this".
- **Extrinsic motivation** (External rewards, Carrot): Doing something for what it gets you: points, loot, money, a badge, or avoiding a penalty. Described as: "I only play for the rewards", "doing it for the loot", "grinding for the unlock", "I do not even like this part but it pays well".
- **Self-determination theory** (SDT, Autonomy, competence, relatedness): Edward Deci and Richard Ryan's theory that people thrive when three needs are met: autonomy (it was my choice), competence (I am getting good at this) and relatedness (other people matter here). Described as: "why does having choices make it more fun", "I want to feel like it was my decision", "I like seeing myself get better", "why does it matter that other people are there".
- **Overjustification effect** (Undermining effect, Crowding out): Rewarding people for something they already enjoy can make them do less of it once the reward stops. They come to see the reward as the reason they were doing it. Described as: "I liked it until it started giving me rewards", "getting paid for it ruined it", "rewards made it feel like a job", "when the rewards stopped I stopped caring".
- **Flow** (In the zone, Flow channel, Flow state): The state of being fully absorbed in a task that stretches your ability without overwhelming it, so that time seems to pass differently. Mihaly Csikszentmihalyi described it from interviews and experience sampling, from 1975 onward. Described as: "I lost track of time playing", "in the zone", "hard enough but not too hard", "the difficulty was just right", "I forgot to eat".
- **Fiero** (Triumph, Hard fun): The burst of triumph after beating something hard, often with arms in the air. Nicole Lazzaro used the Italian word for pride in her 2004 "Four Keys to Fun" research, where it is the reward of what she called hard fun. Described as: "I jumped up and cheered when I finally beat it", "beating a hard boss feels amazing", "the rush of finally winning", "I shouted at the screen in triumph".
- **Power fantasy** (Empowerment, Horde mode feeling): Designing the game so that the player gets to feel overwhelmingly strong. The enemies exist to be swept aside. Described as: "mowing through hundreds of enemies", "I feel unstoppable", "being overpowered is the fun part", "games where you feel like a god".
- **Bartle's player types** (Achievers, explorers, socialisers, killers, Bartle taxonomy): Richard Bartle's 1996 paper sorted players of MUDs, which are text-based online worlds, into four kinds: achievers, explorers, socialisers and killers. Described as: "what kind of player are you", "some people just want to explore and some want to win", "achievers and killers", "that quiz that tells you your player type".
- **Operant conditioning** (Reinforcement, Reward learning, Shaping): Behaviour followed by a reward becomes more likely, and behaviour followed by nothing or by punishment becomes less likely. B. F. Skinner studied it from the 1930s onward. Described as: "the game trained me to do that", "rewarded for doing the right thing", "I learned it by being rewarded", "why do I keep doing what got me points".
- **Skinner box** (Operant chamber, Reinforcement schedule): A sealed cage with a lever and a food dispenser that Skinner used to study how the timing of rewards changes behaviour. He preferred the name "operant chamber". In games, "Skinner box" is an insult for a game that is mostly a schedule. Described as: "this game is just a Skinner box", "pressing a button for rewards like a rat", "the game feels like an experiment on me", "click, wait, click".
- **Variable reward** (Variable ratio schedule, Random reward, Intermittent reinforcement): Rewards that come after an unpredictable number of actions. It is the same pay on average as a fixed schedule, but you can never tell when the next one lands. Described as: "the next one might be the one", "I cannot stop opening chests", "random loot keeps me playing", "just one more pull", "why is random more addictive than fixed".
- **Compulsion loop** (Core reward loop, Engagement loop): A repeating cycle in which an action earns a reward, and the reward makes the next action possible or more appealing: fight, loot, upgrade, fight something harder. Described as: "one more run", "I keep playing to get the next upgrade", "it never gives me a place to stop", "fight, loot, upgrade, repeat".
- **Near-miss effect** (Near miss, So close): A loss that looks almost like a win, such as two jackpot symbols and a third one row off. The claim is that this feels closer to winning than other losses and makes people play on. Described as: "I was so close", "I almost won so I will go again", "two sevens and the third just missed", "the wheel stopped one short of the prize".
- **Hedonic adaptation** (Hedonic treadmill, Reward fatigue, Getting used to it): Good things stop feeling as good as you get used to them. A reward is felt against what you have come to expect, not on its own. Described as: "the rewards stopped feeling good", "I used to love this drop and now I do not care", "big numbers keep getting bigger", "nothing excites me in this game any more".
- **Endowed progress effect** (Head start effect, Artificial advancement): People work harder towards a goal, and finish it more often, if they are given a head start, even when the amount left to do is the same. Joseph Nunes and Xavier Drèze named it in 2006. Described as: "the bar was already partly full when I started", "they gave me a head start", "two free stamps on the loyalty card", "I felt like I had already begun".
- **Goal gradient** (Goal-gradient hypothesis, Speeding up near the end): Effort rises as you get closer to a goal. Clark Hull proposed it in 1932 and tested it with rats in a runway, which ran faster the nearer they were to food. Described as: "I am almost there so I will keep going", "I rush at the end of the bar", "just two more to finish", "I speed up as I get close".
- **Zeigarnik effect** (Unfinished business, Ovsiankina effect (the resuming half)): The claim, from Bluma Zeigarnik's experiments published in 1927, that people remember unfinished tasks better than finished ones. Her colleague Maria Ovsiankina reported the related urge to go back and finish. Described as: "I cannot stop thinking about that quest I left", "I need to finish what I started", "an unfinished level bugs me", "I have to clear the notification".
- **Completionism** (Completionist, 100%, Collect-a-thon, Coupon collector): The urge to finish everything a game offers: every item on the checklist, every marker on the map, the number to 100%. Described as: "I have to get 100%", "I cannot leave a marker on the map", "I need every single collectable", "that last missing item is driving me mad".
- **Curiosity gap** (Information gap, Mystery box): The itch of knowing that there is something you do not know. George Loewenstein described curiosity in 1994 as a gap between what you know and what you want to know. Described as: "I just had to know what was behind that door", "what is in the locked room", "I kept playing to find out what happened", "a mystery that nagged at me".
- **Loss aversion** (Loss framing, Gain framing, Framing effect, Prospect theory): Losing something hurts more than gaining the same thing feels good. Daniel Kahneman and Amos Tversky built this into prospect theory in 1979, and in 1981 showed that wording alone can flip a choice. Described as: "losing it hurts more than winning it felt good", "I hated the penalty but I would like a bonus", "the same thing sounds worse when you put it that way", "I cannot bear to lose my streak".
- **Sunk cost fallacy** (Sunk cost, Already paid, In too deep): Carrying on with something because of what you have already put in, even though that is gone whatever you do next. Only what comes from here on should count. Described as: "I have put too many hours in to quit now", "I already spent so much on this", "I do not even enjoy it but I have come this far", "throwing good money after bad".
- **Endowment effect** (Ownership bias, Mine is better): People value a thing more once they own it. Kahneman, Knetsch and Thaler's 1990 study gave students mugs, and owners asked about twice what others would pay for the same mug. Described as: "I got attached to my character", "I would never sell it now that it is mine", "it is worth more to me because it is mine", "I named my soldier and now I cannot let them die".
- **Gambler's fallacy** (Due for a win, Law of averages): Believing that a run of one outcome makes the other more likely next, when each roll is independent. After five misses, a true 50% shot is still 50%. Described as: "I have lost five in a row so I am due", "the odds must be rigged", "it has to land soon", "it cannot miss again".
- **Fudged odds** (True hit, Hidden assist, Lying about probability): Players read probability badly, so games often show one number and use another. A shown 75% may really be 88%. Described as: "it said 90% and I missed", "the game lies about the odds", "95% chance and it still failed", "players do not understand probability".
- **Peak-end rule** (Duration neglect, End on a high): People judge a past experience largely by its most intense moment and how it ended, and they pay surprisingly little attention to how long it lasted. Kahneman and colleagues showed it with cold water in 1993, and with colonoscopy patients in 1996. Described as: "the ending made the whole game worth it", "I only remember the best bit", "a bad ending ruined the whole game", "I forgot how long the boring part was".
- **Attribution of failure** (Attribution theory, Fair death, That was my fault): What people decide caused their failure: themselves or the game, something they can change or something they cannot. Bernard Weiner built this into a theory of motivation in the 1980s. Described as: "that death was totally fair", "the game cheated me", "I know exactly what I did wrong", "it feels cheap when I die there".
- **Cognitive load** (Mental load, Working memory limit, Too much at once): How much a person has to hold in mind at once. John Sweller developed cognitive load theory in 1988, from research on how people learn. Described as: "too much is going on at once", "I cannot keep track of all this", "the tutorial dumped everything on me", "too many icons on the screen".
- **Mental model** (What the player thinks is going on, Player's theory of the game): The picture a player builds of how the game works. It is only ever a guess, and it steers everything they try next. Described as: "I thought it worked differently", "I do not get what the game wants me to do", "players keep doing the wrong thing", "I have a theory about how this works".
- **FOMO** (Fear of missing out, Limited-time pressure, Daily login pressure): The worry that you are missing something other people are getting. Przybylski and colleagues gave it a formal scale in 2013. In games it is deliberately created by things that will not come back. Described as: "I have to log in or I will miss it", "it is only here for two weeks", "I am scared of falling behind", "the event ends soon and I have not finished".
- **Dark pattern** (Deceptive design, Manipulative design, Roach motel, Confirmshaming): A design that gets people to do something they would not choose if they saw clearly. Harry Brignull coined the term in 2010. Zagal, Björk and Lewis applied it to games in 2013. Described as: "the game tricked me into buying", "I cannot find how to cancel", "the no button is tiny and the yes button is huge", "it made me feel guilty for saying no".

## Story

- **Agency** (Player agency, Meaningful choice): The player's power to change what happens in a way that matters to them. It is measured by what is different afterwards, not by how many buttons were offered. Described as: "my choices actually change things", "nothing I do matters in this game", "the game plays itself and I just watch", "the feeling that you caused what happened".
- **Ludonarrative dissonance** (Story and gameplay clash): What the rules make you do contradicts what the story says is going on. Clint Hocking named it in 2007 in a blog post about BioShock. Described as: "the story says one thing and the gameplay does another", "a nice guy in cutscenes who kills hundreds of people in the game", "the character would never do what the game makes me do", "the urgent mission waits while I play cards".
- **Ludonarrative harmony** (Ludonarrative resonance): The rules and the story say the same thing, so playing the game is itself the telling of the story. Described as: "the gameplay and the story fit perfectly", "dying makes sense in the story", "the mechanics themselves tell the story", "the rules mean what the plot means".
- **Emergent narrative** (Embedded narrative (its opposite), Player stories, Systemic storytelling): Embedded narrative is written in advance and waits to be found, as a cutscene or an audio log. Emergent narrative comes out of the rules running, so players end up telling stories nobody wrote. Henry Jenkins set out both in a 2004 essay. Described as: "stories that happen by accident", "that enemy keeps coming back and remembers me", "nobody wrote this but it was the best bit", "the story came from the systems, not the script", "pre-written story you find in the world".
- **Show, don't tell** (Show don't tell): Let the audience see a thing happen instead of being informed of it. Games have a stronger form: let the player do it. Described as: "the game keeps explaining things I could see", "too much exposition", "a character explains what is already obvious", "let me see it happen instead of telling me".
- **Environmental storytelling** (Staged spaces, What happened here): Arranging a place so that the player works out what happened there. Don Carson brought the idea to games in a 2000 article, borrowing it from theme park design. Described as: "you can tell what happened just by looking at the room", "a skeleton positioned to tell a story", "the room tells a story without words", "working out what happened from clues in the scene".
- **Branching narrative** (Branching story, Choose your own adventure, Time cave): The story splits at each choice into separately written paths. Pure branching never rejoins, so every decision really does send you somewhere else. Described as: "the story splits depending on what I pick", "my choice changes which story I get", "choose your own adventure", "I missed a whole part of the game because of a decision".
- **Branching explosion** (Combinatorial explosion, Geometric explosion): Each extra layer of choices multiplies the writing. Two options per scene, ten choices deep, is 2,047 scenes, and one playthrough reads eleven of them. Described as: "how much do I have to write for all these choices", "the story tree gets too big", "every choice doubles the work", "why games cannot have endless branching".
- **Foldback** (Branch and bottleneck, Bottleneck, Gated branching): Branches rejoin at a shared scene, so the writing stays affordable. Flags carry what you did through the join. Chris Crawford named it, and he thought it cheated. Described as: "different choices lead to the same place", "the paths split and come back together", "the story always ends up back on track", "the plot funnels you to the same scene".
- **Illusion of choice** (Fake choice, Choice without consequence): The player picks between options that all lead to the same thing, with the difference limited to a line or two. It feels like a decision until someone replays it. Described as: "my choice did not actually change anything", "all the options lead to the same result", "I reloaded and it turned out the same", "the game only pretends I have a choice".
- **String of pearls** (Rivers and lakes, Beads on a string): A fixed sequence of open areas. Inside each pearl you can roam and do things in any order. The string between them is the plot, always in the same order. Described as: "open areas connected by a fixed story", "you can explore each level but the order never changes", "linear but with room to wander", "the plot only moves on when you leave the area".
- **Hub and spoke narrative** (Hub structure, Spoke and hub): A central place the player keeps returning to, with separate stories leading off it that can be taken in any order. Described as: "a central base you keep coming back to", "you can do the missions in any order", "levels leading off from one main area", "returning to the same place between missions".
- **State tracking** (Flags, Story variables, Quality-based narrative): The game keeps a list of what has happened: did you pay, who did you lie to, how many times have you died. Scenes then read that list to decide what to say. Described as: "the game remembers what I did earlier", "a character mentions something I did hours ago", "the game forgot I already did that", "how does the game keep track of my choices".
- **Dialogue tree** (Conversation tree, Dialogue wheel, Branching dialogue): A conversation laid out as lines and replies: you pick what to say, the character answers, and new options open or close depending on what has been said. Described as: "pick what to say from a list", "conversation options", "clicking through all the dialogue options", "new things to say appear after you ask something".
- **Barks** (Ambient dialogue, Reactive dialogue, Dynamic dialogue): Short lines characters say by themselves in response to what is happening: "Reloading!", "That was close." The trigger comes from game state, not from a script. Described as: "characters shout things while you play", "enemies say the same line over and over", "my companion comments on what I am doing", "little voice lines that react to the game".
- **Cutscene** (Cinematic, In-engine scene): A stretch of the game that takes control away and plays like a film. It gives you exact framing and timing, at the cost of the player doing nothing. Described as: "the game takes control away and plays a movie", "I just want to skip this scene", "long stretches where I only watch", "a movie in the middle of the game".
- **Quick time event** (QTE, Press X to not die): A button prompt pops up during a scene, and you have a moment to press it. The name comes from the "quick timer events" in Shenmue's manual, though Dragon's Lair played this way back in 1983. Described as: "press a button quickly during a cutscene", "a prompt suddenly appears and I die", "I had to put my drink down during a cutscene", "mash X to open the door".
- **Diegetic** (In-world, Inside the fiction, Diegesis): Something that exists inside the story's world, so the characters could see or hear it. A radio playing in the room is diegetic. The film score is not. Described as: "the health bar is part of the character", "the character can see it too", "no HUD, the information is in the world", "music that comes from a radio in the scene".
- **Avatar versus character** (Silent protagonist, Player character, Blank slate): An avatar is a blank the player fills: they are the hero. A character is someone else with their own past and voice, whom the player steers. A silent protagonist is the usual way to keep the blank blank. Described as: "the main character never talks", "I am meant to be the hero myself", "the hero said something I would never say", "the character has their own personality and I just steer".
- **Narrative design** (Narrative designer, Game writing (the neighbouring job)): Deciding how the story works as a game: what the player learns when, what a choice can change, which systems carry which beats. Game writing is producing the words themselves. Described as: "who decides how the story works in a game", "the writing is good but the story does not work as a game", "the job of fitting a story into gameplay", "difference between a game writer and a narrative designer".
- **Quest** (Mission, Side quest, Task): A unit of story with a goal, some obstacle and an outcome, tracked by the game. A side quest is one the main plot does not require. Described as: "optional missions on the side", "a list of things I can do in my journal", "someone gives me a task with a reward", "stories that are not part of the main plot".
- **Fetch quest** (Go-and-get quest, Courier quest): A quest whose whole content is going somewhere, getting a thing and bringing it back. Described as: "go get this and bring it back", "the game keeps sending me to collect things", "it is just walking back and forth", "errand quests that feel like padding".
- **Three-act structure** (Inciting incident, Setup, confrontation, resolution): A story in three parts: set up a normal life until an inciting incident breaks it, struggle with the consequences, then resolve them. Syd Field made the shape standard in screenwriting. Described as: "beginning middle and end", "the event that kicks off the story", "when does the plot actually start", "the game drags before anything happens".
- **Hero's journey** (Monomyth): A plot pattern set out by Joseph Campbell in The Hero with a Thousand Faces (1949): a call to adventure, a crossing into the unknown, an ordeal, and a return home changed. Described as: "the chosen one goes on an adventure and comes home changed", "the classic hero story", "the mentor dies and the hero goes on alone", "the plot every fantasy game has".
- **Kishotenketsu as a story form** (Four-act structure, Ki-sho-ten-ketsu): A four-part form from Chinese and Japanese writing: introduce, develop, twist, reconcile. The drama comes from a turn that changes how you see the earlier parts, so it needs no conflict at all. Described as: "a story with a twist but no villain", "a story without conflict", "four-panel comic structure", "the last part makes you see the first part differently".
- **In media res** (Into the middle of things, Cold open): Starting the story partway through the action and explaining how you got there later. The Latin means "into the middle of things" and comes from Horace. Described as: "the game starts in the middle of the action", "it opens with a big scene and then goes back", "we start right in the chaos", "how did I get here, the game explains later".
- **Stakes** (What is at risk, What you stand to lose): What will be lost if the hero fails, and what makes that matter to this particular player. Small and personal usually beats vast and abstract. Described as: "I do not care what happens to the world", "what do I lose if I fail", "the game says it is urgent but it does not feel like it", "why should I care about this".
- **Chekhov's gun** (Plant and payoff, Setup and payoff, Foreshadowing): If something is made prominent early, it should matter later. It comes from Anton Chekhov's advice that a loaded rifle on stage has to go off. Described as: "something shown earlier turned out to matter", "that thing from the start came back", "the solution came out of nowhere", "the game set it up hours before".
- **MacGuffin** (Plot coupon, The thing everyone wants): An object that everyone in the story is chasing, whose actual nature hardly matters. Alfred Hitchcock made the word famous. Described as: "everyone is after some magic object", "collect the seven crystals", "it does not matter what the thing does", "the object only exists to move the plot along".
- **Dramatic irony** (Audience knows more, The bomb under the table): The audience knows something the characters do not. Alfred Hitchcock's example: a bomb under a table is fifteen seconds of shock if it is a surprise, and fifteen minutes of suspense if you have seen it. Described as: "I know something the character does not", "I want to warn them", "the audience sees the danger first", "watching them walk into a trap".
- **Unreliable narrator** (Lying narrator): The one telling you the story is wrong, biased or lying, and you are meant to catch them at it. Described as: "the narrator is lying to me", "the story the game tells does not match what I saw", "you cannot trust the character telling this", "the narrator changes the story as he goes".
- **Morality system** (Karma, Good and evil meter, Paragon and Renegade): The game scores your actions on a good-and-evil scale, then changes how the world treats you. It turns ethics into a number, and players treat numbers as things to win. Described as: "the game gives me good and evil points", "I picked the option because it gave the most points", "red and blue dialogue options", "I am being nice for the reward".
- **Multiple endings** (Branching endings, True ending): The story can finish in more than one way, depending on what the player did. The choice may be made in the final minute or built up over the whole game. Described as: "the game ends differently depending on what I did", "I got the bad ending", "how do I get the true ending", "the ending came down to one last button".
- **New Game Plus** (NG+, Second playthrough): After finishing the game, you start over and keep something from the first run, such as your levels, items or knowledge. Described as: "start over but keep my stuff", "playing through again with everything unlocked", "replay the game at a higher level", "something only appears on the second playthrough".

## Worldbuilding

- **Setting** (Backdrop, Time and place): Where and when the game takes place, and the conditions of life there. It decides what can happen, who is around and what everyone takes for granted. Described as: "where and when the game takes place", "the time and place of the story", "the world the game happens in", "it could be set anywhere, it feels generic".
- **Lore** (Backstory, Mythos): Everything known about the world beyond the immediate plot: its history, gods, wars and customs. Players usually meet it in pieces and mostly optionally. Described as: "the background history of the world", "I love reading about the history of this game", "wiki pages of backstory", "optional text about the world".
- **Canon and retcon** (Canon, Retcon, Retroactive continuity): Canon is what officially counts as having happened in the world. A retcon changes that after the fact, so something established is now said to have been different. Described as: "they changed the backstory later", "does this count as what really happened", "the sequel contradicts the first game", "the official version of events".
- **World bible** (Story bible, Series bible, Lore document): The reference document that holds the true answers about your world: the timeline, the names, the rules, how things are spelled. It is written for the team, not for players. Described as: "one document with all the facts about the world", "how do the writers keep the facts straight", "different writers contradict each other", "where do we write down the rules of the world".
- **Iceberg principle** (Theory of omission, Iceberg theory): Know far more about your world than you show. Hemingway's version: an iceberg moves with dignity because only one-eighth of it is above water, and the rest can be felt. Described as: "it feels like there is so much more to this world", "the game hints at things it never explains", "do not explain everything", "too much exposition about the history".
- **Internal consistency** (World logic, Consistent rules): The world obeys its own rules every time, whatever those rules are. A world can be as strange as you like, as long as it stays strange in the same way. Described as: "the game breaks its own rules", "that does not make sense in this world", "the rule worked before, why not now", "the magic only works when the plot needs it".
- **Suspension of disbelief** (Willing suspension of disbelief): The player agrees to accept things that are not true, in exchange for a story. Samuel Taylor Coleridge named it in 1817. Described as: "it pulled me out of the game", "I can accept dragons but not this", "going along with something unrealistic", "it broke my immersion".
- **Verisimilitude** (The appearance of truth, Believability): The quality of seeming true, which is not the same as being true. Small, specific details make a made-up thing feel as if it has been observed. Described as: "it feels real even though it is made up", "tiny details that make the world believable", "it does not have to be realistic, just convincing", "that little detail sold it for me".
- **Tone** (Mood, Register): The attitude a work takes to its own events: grim, silly, cosy, cruel. The same facts can be told in any tone and produce a different game. Described as: "the mood of the game", "it cannot decide if it is funny or serious", "the joke did not fit the scene", "how the game feels about its own story".
- **High concept** (Hook, Elevator pitch, One-line premise): A premise so clear it can be understood and wanted from one sentence. It gives everyone on the team the same picture of the game. Described as: "explain the game in one sentence", "what is the hook", "an idea you get straight away", "what is the elevator pitch".
- **Factions** (Guilds, Reputation groups, Sides): Groups with their own goals, beliefs and grudges, often against each other. Helping one usually costs you with another. Described as: "helping one side makes another side hate me", "different groups in the world with their own goals", "the guilds are at war", "choosing a side".
- **Hard and soft magic** (Sanderson's First Law, Magic systems): Hard magic has clear rules the audience knows. Soft magic stays mysterious. Brandon Sanderson's First Law: an author's ability to solve conflict with magic is directly proportional to how well the reader understands it. Described as: "the magic only works when the plot needs it", "how does the magic actually work", "the hero suddenly has a new power that saves the day", "a clever use of rules I already knew".
- **History layers** (Strata, Layered ruins, Deep time): A place that shows several past eras at once: a modern town on an older town on something older still, each leaving marks the next one built around. Described as: "ruins built on top of older ruins", "you can see the history in the place", "old things in the world nobody explains", "the world feels ancient".
- **Ecology** (Ecosystem, Food chain): What everything in the world eats, and what eats it. A place with real ecology has creatures with reasons to be where they are, doing things unrelated to you. Described as: "the monsters fight each other", "animals have their own lives in the game", "the creatures do things even when I am not there", "what do these monsters even eat".
- **Used future** (Lived-in world, Dirty sci-fi, Wear and tear): A world whose things are old, dented and repaired, so they seem to have been in use for years. George Lucas used the phrase about Star Wars in 1977, and it applies to any setting, not only the future. Described as: "everything looks too clean and new", "it looks like people actually live here", "old battered technology", "scuffed and repaired spaceships".
- **Naming** (Naming language, Phonotactics, Name generator): Naming people and places using a consistent set of sounds, so that they sound as if they come from one culture. The rules for which sounds can sit together are called phonotactics. Described as: "all the fantasy names sound the same", "names that sound like they come from one culture", "generate names that fit together", "too many apostrophes in the names".
- **Conlang** (Constructed language, Fictional language): A language invented for a work, with its own sounds, grammar and words. Real ones are also given a history, with sound changes that split one old tongue into several new ones. Described as: "a made-up language in a game", "the characters speak a language that does not exist", "an invented alphabet you can learn to read", "two languages that are clearly related".
- **In-world documents** (Audio logs, Item descriptions, Found text, Collectible lore): Letters, audio logs, signs and item descriptions that exist inside the fiction. Each is written by someone, for someone, for a reason, and that is what makes them feel found and not delivered. Described as: "reading the item descriptions for the story", "audio logs lying around", "finding notes and diaries in the world", "the story hidden in collectibles".
- **Cultural texture** (Customs, Everyday culture, Anthropology): The ordinary habits that make a people particular: what they eat, how they greet each other, what is rude, what they swear by. It is mostly small and rarely explained. Described as: "every town in this game feels the same", "little customs that make a place feel foreign", "the people here have their own way of doing things", "it feels like a real culture".
- **The map as a story** (Map logic, Geography as history, Fantasy map): Geography explains history: towns grow at river crossings, borders follow mountains, roads go around the marsh. A map that follows those reasons tells a story before anyone speaks. Described as: "why is there a town in the middle of nowhere", "the map makes sense", "the geography tells you the history", "looking at the map and imagining the place".
- **Fridge logic** (Icebox scene, Plot hole you notice later): Something that seemed fine at the time, and only falls apart later, when you are at the fridge and have stopped to think. Alfred Hitchcock is credited with calling these icebox scenes. Described as: "it only hit me later that it made no sense", "wait, why did they not just do that instead", "that seemed fine until I thought about it", "a plot hole I noticed afterwards".
- **Scale** (Compressed space, Game scale): How big the world claims to be against how big it actually is. Game worlds are heavily compressed: a capital of thousands is a few streets, and a kingdom takes an afternoon to walk. Described as: "this capital city only has twelve houses", "the world feels too small", "I crossed the whole kingdom in ten minutes", "how big should the map be".

## Looks

- **Art direction** (Visual direction, Art style, Visual identity): The set of decisions that makes every picture in a game look as if it belongs to the same game: palette, shapes, lighting, level of detail, how things move. An art director writes those rules and holds everyone to them. Described as: "every screen looks like the same game", "the art feels inconsistent", "choosing the overall look of the game", "it looks like a mix of different asset packs".
- **Stylisation** (Stylised art, Abstraction): Deliberately leaving out and exaggerating parts of reality so that what remains says more. A stylised tree is not a worse tree; it is a choice about which few things make a tree. Described as: "it does not try to look real", "cartoony look instead of realistic", "simplifying things so they look better", "why old stylised games still look good".
- **Readability** (Visual clarity, Legibility, Read): How quickly a player can tell what they are looking at and what it means for them: what can hurt me, what can I touch, where can I stand. Artists say a thing "reads" when it is understood in a glance. Described as: "I got hit by something I could not see", "the screen is too busy", "I cannot tell what is background and what is dangerous", "enemies blend into the level".
- **Silhouette** (Silhouette test, Outline read): The outline of a character or object, filled in solid. The silhouette test asks whether you can still tell who it is with all colour and interior detail gone. Described as: "I cannot tell the characters apart", "telling who is who from far away", "all the characters have the same body", "recognising a character just from its shape".
- **Value structure** (Squint test, Value, Light and dark pattern, Notan): The pattern of light and dark in a picture, ignoring colour. Value means how bright a colour is. The squint test is the old painter's check: narrow your eyes until detail goes, and see whether the picture still holds together. Described as: "the picture looks muddy", "squinting at the screen to check it", "it looks fine in colour but flat in black and white", "everything is the same brightness".
- **Focal point** (Point of interest, Visual hierarchy, Leading the eye): The one place the eye lands first. You make it with the strongest contrast, the only saturated colour, an isolated shape, or lines that point at it. Described as: "I do not know where to look", "the game shows me where to go without an arrow", "making something stand out", "drawing the eye to one thing".
- **Shape language** (Shape design, Circles, squares, triangles): Building a design out of one family of simple shapes so that it carries a meaning before any detail. Circles tend to read as friendly, squares as sturdy, and triangles as dangerous or quick. Described as: "the enemy just looks dangerous", "round characters seem friendly", "spiky means bad", "why does this character look evil".
- **Palette** (Colour palette, Limited palette, Swatches): The fixed set of colours a game, a level or a character is allowed to use. Old hardware forced a small one; artists now often choose one anyway. Described as: "using only a few colours", "the colours all go together", "the art looks messy and rainbow-coloured", "choosing the colours for the game".
- **Colour harmony** (Colour scheme, Colour wheel, Complementary colours): Choosing colours by where they sit on the colour wheel. Neighbours (analogous) feel calm, opposites (complementary) feel tense and bright, and three spaced evenly (triadic) feel playful. Described as: "which colours go together", "the colours clash", "orange and blue look good together", "why does this colour scheme feel calm".
- **Colour script** (Colour keys, Mood strip, Color script): The whole story laid out as a strip of small paintings, one per beat, so you can read its emotional arc as colour before anything is built. It answers: what does each part of this feel like, and how does it change? Described as: "the mood of the game changes with the colours", "planning the colours of the whole story", "every level looks the same", "a strip of pictures showing the mood of each part".
- **Foreground framing** (Framing, Foreground elements, Natural frame): Placing dark shapes close to the camera, such as branches, rocks or a doorway, around the edge of the view so they frame what matters. Described as: "branches or rocks in front of the camera", "looking through a doorway at the view", "shapes around the edge of the screen", "making the scene feel deeper".
- **Atmospheric perspective** (Aerial perspective, Depth haze): Far things look paler, bluer and lower in contrast, because there is more air between you and them. Painters have used this for centuries to make a flat surface look deep. Described as: "far away things look pale and blue", "mountains fade into the sky", "making the background feel far away", "the background competes with the foreground".
- **Parallax** (Parallax scrolling, Layer scrolling): Background layers move slower than the foreground as the camera moves, the same way that fence posts rush past a train window while hills barely shift. It fakes depth on a flat screen. Described as: "the background moves slower than the foreground", "layers scroll at different speeds", "the 2D game looks like it has depth", "it feels like paper sliding around".
- **Pixel art** (Sprite art, 8-bit style, 16-bit style): Art made at a low resolution with every pixel placed on purpose, then shown enlarged with hard edges. Each pixel is a decision, which is what separates it from a shrunken image. Described as: "the blocky retro look", "you can see each pixel", "making a new game look like an old one", "the pixels are all different sizes".
- **Palette swap** (Recolour, Colour swap, Palette shift): The same image data shown with a different set of colours. The picture stores numbers that point into a palette, so changing the palette recolours everything at once and costs no extra art. Described as: "the same enemy in a different colour", "the red one is stronger than the blue one", "the clouds and bushes are the same shape", "a second player who looks identical except for colour".
- **Dithering** (Ordered dither, Bayer dither, Error diffusion, Floyd-Steinberg): Faking colours you do not have by mixing dots of the ones you do. From a distance, a checkerboard of black and white looks grey, so a smooth gradient survives a tiny palette. Described as: "the checkerboard pattern in old games", "gradients made of dots", "the sky has ugly stripes in it", "fake shading with only two colours".
- **Sprite** (Sprite sheet, Sprite strip, Flipbook): A 2D image drawn into the game at some position, usually a character or object. A sprite sheet is one image holding all its frames; playing the animation means showing a different rectangle of it each moment. Described as: "one image with all the frames of a character", "how 2D characters are animated", "the character jitters when it animates", "a picture that moves around the screen".
- **Tileset** (Tilemap, Autotile, Tile bitmask): A set of small square images that fit together edge to edge, used to build big levels from a small amount of art. Autotiling picks the right edge or corner piece for you by checking each tile's neighbours. Described as: "the level is built from squares", "the edges and corners get picked automatically", "I can see the same tile repeating", "painting levels on a grid".
- **Texture atlas** (Atlas, Sprite atlas, Texture packing): One big image with many smaller images packed into it. Switching images is slow for a graphics card, so if everything lives in a single image the game can draw it all in one go. Described as: "one big image holding all the small images", "too many draw calls", "lots of little textures slow the game down", "packing images together".
- **Low poly** (Polygon count, Flat shaded, Poly count): Models built from few triangles, with the facets left showing. Once a hardware limit, it is now often a chosen style, because each flat face catches light as a single colour. Described as: "models made of visible triangles", "the faceted look", "simple 3D without textures", "how many polygons should a character have".
- **PBR** (Physically based rendering, Metalness and roughness, Physically based shading): Shading materials by rules of real light, usually described with two main numbers: how rough a surface is and whether it is metal. Because the material is described and not painted, it looks right under any light. Described as: "materials look right in any lighting", "it looks like real metal", "roughness and metalness maps", "the highlights are painted on".
- **Normal map** (Bump map, Surface detail map): A texture that stores which way the surface faces at every pixel, as a colour. Lighting reads it, so a flat wall gets the shading of bricks and cracks while the geometry stays flat. Described as: "it looks bumpy but it is flat", "the bricks catch the light but the wall is flat", "the purple textures", "fake detail on a simple model".
- **Cel shading** (Toon shading, Toon shader): Shading in a few flat steps of colour instead of a smooth gradient, often with an ink outline, so a 3D model looks like a hand-painted animation cel. Described as: "the 3D game looks like a cartoon", "flat shadows with hard edges", "it looks like an anime", "black outlines around 3D characters".
- **Rim light** (Rim lighting, Back light, Edge light, Fresnel highlight): A thin line of light along the edge of a shape, as if something bright stands behind it. In games it is often calculated: the more a surface turns away from you, the brighter it gets. Described as: "the glowing line around a character", "the character is lost in the dark", "light from behind the character", "making a character stand out from the background".
- **Ambient occlusion** (AO, SSAO, Contact shadow): Soft darkening where surfaces meet: in creases, corners and under objects, where less of the surrounding light can reach. It is a shadow with no particular light causing it. Described as: "dark soft shadows in the corners", "objects look like they are floating", "things do not feel grounded", "darkening where two walls meet".
- **Bloom** (Glow, Light bloom, Real-time glow): Bright parts of the picture bleed soft light into the pixels around them, the way light scatters in your eye or in a camera lens. It works by copying the brightest pixels, blurring them, and adding them back. Described as: "lights have a soft glow around them", "bright things look like they are glowing", "the whole game looks hazy and washed out", "neon signs that glow".
- **Colour grading** (LUT, Lookup table, Post-processing colour): Shifting all the colours of the finished picture to set a mood, as a last step. A LUT, or lookup table, stores the shift as a small cube of colours: each input colour simply looks up its output. Described as: "the whole game has a green tint", "a colour filter over everything", "changing the mood without changing the art", "the orange and teal film look".
- **Mipmap** (Mip levels, Mips, Trilinear filtering): A stack of smaller, already blurred copies of each texture, and the graphics card picks the size that fits how far away the surface is. "Mip" comes from the Latin multum in parvo, much in a small space. Lance Williams described it in 1983. Described as: "far away textures shimmer and sparkle", "the floor looks noisy when I move", "textures crawl in the distance", "old 3D games have sizzling textures".
- **Skybox** (Sky dome, Cube map, 3D skybox): A giant picture of the distant world wrapped around the camera, usually on the inside of a cube, and drawn behind everything else. It moves with you, so you can never get closer to it, which is how it seems infinitely far away. Described as: "the mountains never get closer", "the sky is just a big picture", "I can see the corners of the sky", "the background follows me around".
- **Billboarding** (Billboard, Impostor, Camera-facing sprite): A flat picture in a 3D world that keeps turning to face the camera, so you never catch it edge-on. Trees, grass, particles and old-style enemies are often done this way. Described as: "the trees turn to follow me", "flat sprites in a 3D game", "old shooter enemies always face you", "the grass is just flat pictures".
- **The twelve principles of animation** (Twelve basic principles, Disney's principles): Twelve rules for making drawings seem alive, worked out by Disney's animators and set down by Frank Thomas and Ollie Johnston in their 1981 book The Illusion of Life. They are still how animators talk about motion. Described as: "the animation looks stiff", "the rules of good animation", "why does this motion feel lifeless", "the Disney animation rules".
- **Timing and spacing** (Easing, Slow in, slow out, Ease in and out): Timing is how many frames a move takes. Spacing is how far it travels between each of those frames. Same timing with different spacing gives very different motion. Described as: "the animation looks robotic", "it moves at the same speed all the way", "it should start fast and slow down", "easing".
- **Pose to pose** (Keyframing, Key poses, Inbetweening, Tweening): Drawing the most important poses first, then filling in the frames between them. Its opposite is straight ahead, drawing each frame after the last from start to finish. Described as: "setting the main poses first", "keyframes", "the computer fills in the frames between", "drawing it from start to finish without planning".
- **Animating on twos** (On ones, On twos, Limited animation, Held frames): Showing each drawing for two frames of a 24-frame second, so there are 12 new drawings a second. "On ones" means a new drawing every frame, and "on threes" every third. The holds are a choice, not a slowdown. Described as: "the character moves choppily but the game is smooth", "the anime look with fewer frames", "held frames", "why does the character look like a flipbook".
- **Smear frames** (Smear, Motion smear, Multiples): One or two distorted drawings, shown so briefly you never quite see them, that stretch an object along its path during a very fast move. It is the hand-drawn version of motion blur. Described as: "the weird stretched frame if you pause a fast cartoon", "the swing looks like it teleports", "one frame of the sword turns into a crescent", "hand-drawn motion blur".
- **Skeletal animation** (Frame-by-frame animation, Bone animation, Cutout animation, Traditional animation): Two ways to make a character move. Frame by frame means a new drawing for each pose. Skeletal means one drawing (or model) attached to bones, with the computer moving the bones. Described as: "it looks like a paper puppet", "hand-drawn frames or bones", "the character is made of parts that rotate", "can we reuse the animation on another character".
- **Rigging** (Rig, Inverse kinematics, IK, Forward kinematics, FK): Building the skeleton and the controls that move a character. With forward kinematics you rotate each joint in turn, from the shoulder down. With inverse kinematics you place the hand, and the solver works out the joints. Described as: "the feet float above the stairs", "the hand does not reach the door handle", "moving the hand and the elbow follows", "making a character ready to animate".
- **Blend tree** (Blend space, Animation blending, Locomotion blending): A small graph that mixes animations by a number from the game. Feed in speed and it returns, say, 30% walk and 70% run, averaged joint by joint and kept in step, so there is no separate clip for every speed. Described as: "the character pops between walk and run", "smooth change from walking to running", "mixing two animations", "jogging speed that was never animated".
- **Root motion** (In-place animation, Animation-driven movement, Foot sliding): Letting the animation decide how far the character moves. The animator moves the whole body in the clip, and the game follows it. Its opposite is in-place animation, where code moves the character and the clip marches on the spot. Described as: "the feet slide on the floor", "the character looks like it is moonwalking", "the animation controls where the character goes", "the attack moves the character forward".

## Sound

- **Waveforms** (Sine, square, triangle, saw, Oscillator shapes, Timbre): The basic repeating shapes a synthesiser starts from. Each has its own stack of harmonics, the quieter pitches above the main one, and that stack is what makes it sound the way it does. Described as: "why does this synth sound buzzy", "the retro beepy sound", "what kinds of sound can a synth make", "pure tone versus harsh tone".
- **ADSR envelope** (Envelope, Attack, decay, sustain, release, Volume envelope): Four numbers that shape a note's loudness over time. Attack is how fast it rises, decay how fast it falls to the sustain level, and release how long it takes to fade once the note ends. Described as: "the sound starts too abruptly", "how a note fades in and out", "make this sound more plucky", "the sound takes too long to start".
- **Low-pass filter** (LPF, High-cut, Muffling): A filter that lets low frequencies through and cuts high ones above a chosen point, the cutoff. Close it and a sound goes dull, as if heard through a wall. Described as: "make it sound muffled", "the underwater sound effect", "sound through a wall", "music goes dull when you pause".
- **Chiptune** (8-bit music, Chip music): Music written for, or in the style of, the sound chips of old consoles and computers. Those chips have only a few voices, each playing one note at a time, so every limit is heard. Described as: "the 8-bit music style", "old video game music", "beepy retro soundtrack", "music that sounds like an old console".
- **Ambience** (Ambient sound, Atmos, Room tone, Soundscape): The constant quiet sound of a place: a low bed that never stops, plus small sounds scattered at random around you. Nobody notices it until it stops. Described as: "background noises of a place", "the world feels dead and empty", "wind and birds in the background", "the sound of a room".
- **Foley** (Footsteps and cloth, Movement sounds): Sounds of bodies and the things they touch, usually recorded by a person acting them out: footsteps, clothes, a hand on a door. The name comes from Jack Foley, who did this for early film. Described as: "footstep sounds", "the sound of clothes rustling", "sounds change when you walk on different ground", "the character feels weightless because they make no sound".
- **Diegetic and non-diegetic sound** (In-world sound, Source music, Underscore): Diegetic sound exists inside the game's world, so its characters could hear it: a radio, a footstep. Non-diegetic sound lays over the world for you alone: the score, a menu click. Described as: "music that comes from a radio in the game", "can the characters hear this music", "the soundtrack is playing inside the world", "a song the character can turn off".
- **Attenuation** (Falloff, Rolloff, Distance curve): How a sound gets quieter as you move away from it. A curve maps distance to volume, usually with a range inside which it is at full volume and a range beyond which it stops. Described as: "sounds get quieter when you walk away", "I can hear things from too far away", "how far does this sound carry", "the volume drops off with distance".
- **Occlusion** (Muffling through walls, Obstruction, Sound propagation): Muffling a sound because something solid stands between it and the listener, usually with a low-pass filter and a drop in volume. Games test this with lines or room graphs. Described as: "sounds should be muffled behind a wall", "I can hear enemies through walls like they are next to me", "the music from the other room", "sound changes when a door opens".
- **Reverb** (Reverberation, Room sound, Convolution reverb): The thousands of echoes that follow a sound as it bounces around a space, blurred into a tail. Its length and colour tell your ears the size and material of the room. Described as: "the echo in a big room", "it sounds like a cave", "the sound does not match the room", "sound feels dry and flat".
- **Pitch randomisation** (Round robin, Variation, Random container): Playing a repeated sound slightly higher or lower each time, or cycling through several recordings of it, which is called round robin. The two are usually used together. Described as: "the same sound over and over gets annoying", "the machine-gun effect", "footsteps sound robotic", "it sounds like one sample repeating".
- **Voice limiting** (Polyphony limit, Voice stealing, Virtual voices, Max instances): A cap on how many sounds can play at once. When a new sound needs a voice past the limit, the least important one is stopped: it is stolen. Described as: "too many sounds at once", "some sounds cut out when it gets busy", "the audio distorts in big fights", "it gets loud and crunchy when lots happens".
- **Mix** (Mixing, Balance, Snapshot, Bus): The balance of every sound against the others, so that what matters can be heard. In a game it must change as play changes, so groups of sounds get saved sets of levels called snapshots. Described as: "I cannot hear the dialogue over the music", "everything is the same loudness", "it is just a wall of noise", "balancing the volumes".
- **Dynamic range and loudness** (Loudness, LUFS, Compression, Night mode): Dynamic range is the distance from the quietest sound to the loudest, in decibels. Loudness is how loud the whole game seems over time, measured in a unit called LUFS. Described as: "I keep turning the volume up and down", "the explosions are way too loud and the dialogue is too quiet", "the game is much quieter than other games", "night mode for audio".
- **Ducking** (Sidechain, Sidechain compression, Auto-ducking): Turning one sound down automatically while another plays, most often music under speech. A sidechain is the wire that does it: one sound's level controls another's volume. Described as: "the music gets quieter when someone talks", "I cannot hear the dialogue over the music", "the music dips for a big explosion", "sound pumping".
- **Silence as a tool** (Audio rest, Negative space, Dropping out): Removing sound on purpose: cutting the music, or even the ambience, before or during a moment. Silence is something you can play, as long as you have made noise beforehand. Described as: "the music cuts out right before something big", "the quiet before the storm", "it suddenly goes silent and it is scary", "make this moment hit harder".
- **Earcon** (Audio icon, UI sound, Notification sound): A short abstract sound with a learned meaning, like a menu blip that means yes. It is a word in the game's language, and nothing in the real world sounds like it. Described as: "the sound when you click a menu", "the little jingle when you find a secret", "a sound that tells you it worked", "the error beep".
- **Stinger** (Musical sting, Hit point, Musical punctuation): A short burst of music played over the score to mark a moment: a discovery, an alarm, a victory. It is written to fit the score, and can wait for the next beat. Described as: "the music hit when an enemy spots you", "a dramatic sound when something appears", "the sting when you find an item", "a short burst of music for an event".
- **Leitmotif** (Theme, Motif, Character theme): A short tune tied to one character, place or idea, and brought back changed as the story goes. The same notes can be heroic in one key and broken in another. Described as: "the same tune keeps coming back", "a character has their own music", "I recognised that melody from earlier", "the sad version of the main song".
- **Vertical layering** (Vertical remixing, Stems, Layered music): Splitting one piece of music into layers that all play at once in sync, then fading them in and out with the game. The music can change at any moment without a seam. Described as: "drums come in when a fight starts", "the music gets more intense without changing song", "instruments get added as things heat up", "layers of music fading in".
- **Horizontal resequencing** (Branching music, Music states, Transition on the bar): Cutting music into sections and letting the game choose which plays next. Requests wait for a musically sensible point, usually the next bar line, so changes sound written. Described as: "the music changes when you enter a new area", "the song changes smoothly when a fight starts", "music transitions on the beat", "the music cuts awkwardly between tracks".
- **Adaptive music** (Interactive music, Dynamic music, Reactive score): A score that responds to what the player is doing, by bringing layers in and out, moving between sections, or both. The composer writes rules as well as notes. Described as: "the music reacts to what I am doing", "music changes when enemies notice me", "the score follows the play", "the music builds as things get dangerous".
- **Musical feedback** (Rising pitch, Combo pitch, Scale on hits): Playing the sounds of repeated actions as notes, often climbing a scale as a combo grows. The action becomes a tune, and the player can hear how well it is going. Described as: "the sound gets higher with each coin", "each hit plays the next note", "combo sounds that climb", "the collecting sounds make a tune".

## Interface

- **HUD** (Heads-up display, Non-diegetic UI, Overlay): The information laid over the picture of the game: health, ammo, score, map. The name comes from fighter planes, whose pilots read figures on the glass without looking down. Elements that exist only for the player, outside the world, are also called non-diegetic. Described as: "the numbers and bars around the edge of the screen", "health and ammo on screen while you play", "the screen is cluttered with icons", "can I turn off all the stuff on screen".
- **Diegetic UI** (In-world UI, Diegetic interface): Interface that exists inside the game's world, so the character could see it too: a meter on a suit, a map held in the hand. Fagerholt and Lorentzon's 2009 thesis Beyond the HUD names four kinds of game UI, sorted by two questions: is it in the story, and is it in the world's space? Described as: "the health bar is on the character's suit", "the character looks at a real map in their hands", "information that exists in the game world", "no UI, the game world shows you everything".
- **Spatial UI** (World-space UI, Spatial interface): Interface placed in the game's 3D space that the character can't see: an outline round an enemy, a glowing trail on the ground. It exists in the space but not in the story. Described as: "words floating in the world", "a glowing line on the ground showing the way", "an outline around an enemy", "markers that exist in 3D but not in the story".
- **Meta UI** (Meta interface, Screen-space effects): Interface that stands for something in the story but is drawn on the screen rather than in the world: blood on the camera when you're hurt, a phone that fills the screen. It is in the story but not in the space. Described as: "blood on the screen when you get hurt", "the screen goes red when you are nearly dead", "the edges of the screen get darker", "the picture cracks when you are hit".
- **Information hiding** (Hidden information, Withheld stats): Deliberately leaving out a number the game knows, so the player has to read it from the world or work it out. In other words, deciding what the HUD should keep in the fog. Described as: "the game does not show the enemy's health", "I have to work out how hurt it is by watching it", "the game hides the numbers", "fog of the HUD", "I never know how many bullets I have left".
- **Text readability** (Legibility, Contrast, HUD readability): How quickly and reliably someone can read what the interface is telling them while busy doing something else. For text it comes down to size, weight and contrast against whatever happens to be behind it. Described as: "I cannot read the text over the background", "white text on a bright background", "hard to see what is going on", "the words get lost in the picture".
- **UI scale** (HUD scale, Text size, Ten-foot UI): How big the interface is drawn, and usually a setting that lets players change it. What matters is how large it looks from where they sit, which depends on the screen's size and their distance from it. Described as: "the text is too small to read from my sofa", "make the UI bigger", "can't read the words on a TV", "tiny text on the Switch", "menus are fine on my monitor but small on the TV".
- **Safe area** (Title safe, Action safe, Overscan): The part of the picture you can trust a screen to show. Many TVs blow the picture up slightly and crop its edges, which is called overscan, so anything important stays inside a margin. The broadcast standard keeps titles within the middle 90%. Described as: "the HUD is cut off at the edge of my TV", "my TV crops the picture", "text goes off the side of the screen", "the notch covers the score".
- **Health bar** (Life bar, Ghost bar, Delayed health bar, Damage trail): A shape that shows how much damage you can still take. A common refinement is the ghost bar: when you are hit, the chunk you lost stays visible in a paler colour for a moment, then drains away. Described as: "the bar leaves a white part behind when you get hit", "the health bar drains slowly after a hit", "how much did that hit take", "yellow part of the health bar that catches up", "hearts instead of a bar".
- **Damage numbers** (Floating combat text, Hit numbers, Pop-off numbers): Numbers that jump off an enemy each time you hit it. They turn a hidden sum into feedback: how hard, and whether it was a critical hit. Described as: "numbers fly up when you hit something", "how much damage did I do", "floating numbers on enemies", "big yellow number on a critical hit".
- **Minimap** (Radar, Mini-map): A small map in a corner of the screen, showing what's nearby and where you are. It answers "where am I and where do I go?" without opening anything. Described as: "the little map in the corner", "the small map that shows where you are", "I spend the whole game looking at the map", "radar on the screen".
- **Waypoint** (Objective marker, Quest marker, Map pin): A marker that shows exactly where to go next, usually with a distance. It can sit on a compass, on the map or in the world. Described as: "the arrow that tells you where to go", "marker on the screen with distance", "follow the quest marker", "I just follow the icon and never look at the world".
- **Screen edge indicator** (Off-screen indicator, Damage direction indicator, Threat arrow): A mark at the edge of the screen pointing to something important that is off it, such as who just shot you or where your teammate is. Described as: "the arrow that shows where you got shot from", "I got hit from off screen", "what is shooting me", "a marker at the edge of the screen pointing at the enemy".
- **Quest log** (Journal, Mission log, Objectives screen): A screen that keeps track of what you've been asked to do and what you already know. It is the game's memory, so players don't need one of their own. Described as: "the list of what I am supposed to be doing", "I came back after a break and forgot what I was doing", "mission list", "the game does not tell you what quests you have".
- **Inventory** (Backpack, Grid inventory, Carry weight, Item slots): The screen and the rules for what you're carrying. The rule is usually one of three: a set number of slots, a weight limit, or a grid in which each item has a shape. Described as: "the backpack screen", "I have run out of room", "playing Tetris with my items", "you are carrying too much", "too much loot and nowhere to put it".
- **Tooltip** (Hover text, Nested tooltip, Keyword tip): A small box explaining the thing you are pointing at. A nested tooltip goes one further: words inside the box have tooltips of their own. Described as: "the little box that appears when you hover", "I do not know what this word means in the game", "explanation pops up when you point at something", "I keep looking things up on the wiki".
- **Signifier** (Visual language, Yellow paint, Environmental cue): Any perceivable hint that an action is possible here: paint on a ledge, a glowing crack, a handle on a door. Don Norman brought the word into design to separate the thing you can do from the sign that tells you so. Described as: "yellow paint on everything you can climb", "how do I know I can climb that", "the game shows you where to go with colour", "I did not know you could go there", "the cracked wall means you can break it".
- **Fitts's law** (Fitts law, Target size rule): The time it takes to reach a target grows with distance and shrinks with size, in a precise way. Paul Fitts measured it in 1954: time = a + b × log2(2D ÷ W), so doubling the distance or halving the width adds the same fixed amount. Described as: "the button is too small to hit", "big buttons are faster to press", "why are the important buttons so far away", "I keep missing the button on my phone".
- **Menu flow** (Screen flow, UI flow, Wireframe flow): The map of every screen in a game and how you get from one to the next: what Back does, where the cursor lands, what comes after a game over. Described as: "it took me ages to get back to the game", "the cursor keeps going back to the top", "how the menus connect to each other", "why do I have to go through all these screens".
- **Friction** (UX friction, Interface cost, Clicks to do it): Everything that stands between wanting to do something and having done it: presses, waits, confirmations, screens. Some is deliberate, and most of it is an accident nobody noticed. Described as: "it takes too many clicks", "there are so many menus just to do one thing", "annoying to have to do this every time", "why do I have to pause to change boots".
- **Pause** (Pause menu, Real-time menu, Active pause): Stopping the game. It seems too obvious to need a word, except that many choices are hiding here: whether menus stop the world, what happens when the phone rings, and whether the game pauses itself when you lose focus. Described as: "the game keeps going when you open the menu", "I can't pause this game", "I got killed while looking at my inventory", "the game should stop when I alt-tab".
- **Loading screen** (Load time, Loading tips, Playable loading screen): What the player sees while the game reads what it needs from the disc or drive. It can be a blank screen, a progress bar, a tip or even a bit of play. Described as: "the screen you wait at between levels", "the game is taking forever to start", "is it frozen or still loading", "little game to play while it loads", "hints between levels".
- **Onboarding** (First-time user experience, FTUE, New player experience, First session): Everything that takes a stranger to being someone who knows how to play and wants to keep going. The start of that, the first few minutes, is often called the first-time user experience, or FTUE. Described as: "the game takes so long to start", "the first ten minutes of the game", "too many screens before you can play", "getting new players into the game".
- **Tutorial** (Training level, Prompted teaching): A part of the game set aside to explain how to play, usually with instructions. It can be a dedicated level, or short prompts that appear as they're needed. Described as: "the game teaches you the controls", "walls of text explaining how to play", "forced tutorial I can't skip", "a training level at the start".
- **Teaching by doing** (Show, don't tell, Silent teaching, Level as tutorial): Building the level so the player works out a rule for themselves: first a safe place to try it, then a small test, then a real one. No text is needed. Described as: "the game teaches you without telling you", "the level shows you what to do", "I figured it out by myself", "no tutorial but I knew what to do".
- **Button prompt** (Controller glyphs, Input icons, Press A to): The on-screen icon that tells you which button to press. Glyphs are the icons themselves, and they have to match the device in your hands, because pads label the same positions differently. Described as: "the game shows the wrong buttons for my controller", "press A but my controller has no A", "it shows Xbox buttons on my PlayStation pad", "the icon showing what button to press".
- **Input remapping** (Rebinding, Custom controls, Key bindings): Letting players choose which button or key does what. Full remapping covers every action, including the menus. Described as: "I want to change the controls", "can I swap these buttons", "rebind my keys", "the jump button is in a stupid place", "my keyboard layout is different".
- **Subtitles** (Captions, Closed captions, Speaker labels): Dialogue as text on screen. Captions go further, with sounds and music as well. Done well, they come with a choice of size, a background, the name of whoever is speaking, and where that person is. Described as: "I can't read the subtitles", "tiny text at the bottom of the screen", "who is talking", "the words disappear against the background", "playing without the sound on".
- **Colour-blind modes** (Colour vision settings, Never colour alone, Redundant coding, Daltonism options): Settings that change a game's colours for people who see them differently, about 1 man in 12 and 1 woman in 200. The stronger rule goes with it: never let colour be the only thing that carries a meaning, and back it with shape, icon or position. Described as: "I can't tell the red team from the green team", "colour-blind setting", "everything looks the same colour to me", "the only difference between them is the colour".
- **Accessibility options** (Assist mode, Assist options, Difficulty options): Settings that let more people play: for vision, hearing, movement and how fast you can think or react. The good ones change one specific barrier and leave the rest of the game as it is. Described as: "I physically can't do this part", "the game is too fast for me", "make the game playable for me without making it easy", "settings for disabled players", "skip this bit, I have tried enough".
- **Motion settings** (Reduce motion, Motion sickness options, Camera shake setting, Photosensitivity options): Controls over how much the picture moves by itself: camera shake, head bob, motion blur, flashes, field of view. They are for people who get ill or disoriented from on-screen movement, and they should default to the system's reduced-motion setting where one exists. Described as: "this game makes me feel sick", "turn off the camera shake", "the screen moves too much", "motion blur gives me a headache", "the flashing is too much".
- **One-handed play** (One-handed mode, Single-hand control scheme, Thumb-only): A way of playing with one hand, whether for someone who only has the use of one, or for a person holding a baby or a train strap. It usually means merging actions onto fewer buttons and letting the game do some of them for you. Described as: "I can only use one hand", "play this with one hand on the bus", "I have to hold too many buttons", "tap anywhere with my thumb".
- **Save system** (Autosave, Save points, Saving, Save slots): The rules for how your progress is kept: whether by save points, by saving anywhere, or by autosave, where the game writes your progress for you every so often. Each choice sets what a mistake or a crash can cost. Described as: "how often does the game save", "I lost an hour of progress", "the game saves by itself", "the little spinning icon", "do not turn off the console".
- **Checkpoint** (Respawn point, Bonfire, Bench, Mid-level restart): A place in the level that you return to when you die, so you don't have to start over. Its spacing sets the price of every death. Described as: "the game puts you back at the last save point when you die", "I had to replay the whole level", "the bench or bonfire you come back to", "how far back do you go when you die".
- **Quicksave** (Save scumming, Quickload, Save anywhere, Reload abuse): One button that saves right now, and another that takes you back. Save scumming is what people do with it: reloading again and again until the dice fall their way, or until they've got through without a scratch. Described as: "reloading until it goes my way", "pressing F5 every few seconds", "saving before every fight", "it is too easy to just reload", "the same shot misses every time I reload".
- **Attract mode** (Demo mode, Advertise mode, Self-playing demo): What a game does when nobody is playing: shows itself. Arcade cabinets looped their title, scores and a demo that played itself, to pull people in from across the room. This site's home page is doing the same thing right now. Described as: "the game plays itself when no one is touching it", "arcade machine showing the game with insert coin", "the demo on the title screen", "website that shows the game running before you play".

## Genres

- **Genre** (Game type, Category): A family of games that share verbs and a core loop. Film genres are named for mood or setting, such as horror or western. Game genres are usually named for what you do, or after the game that first did it. Described as: "what kind of game is this", "the word for this type of game", "games that all play in a similar way", "it is a bit like a mix of two types of game".
- **Platformer** (Platform game, Jump and run): You move a character through space by running and jumping across gaps and hazards. It promises mastery of your own body: every death is a jump you can see how to do better. Described as: "a game where you run and jump across gaps", "jumping between platforms", "a game like Mario", "you die, you restart, you try the jump again".
- **Metroidvania** (Search action): One large connected map, where new abilities open paths you already saw and could not take. It promises the pleasure of remembering a door. The name joins Metroid and Castlevania. Described as: "you get a new ability and can reach places you saw earlier", "I saw that door hours ago and can finally open it", "a big connected map with locked paths", "going back to old areas with new powers".
- **Bullet hell** (Shmup, Shoot 'em up, Danmaku, Curtain fire): A shooter whose screen fills with slow, patterned enemy fire that you thread through. It promises calm inside chaos. Your real hitbox is far smaller than your ship, which makes it possible. Described as: "the screen is completely full of bullets", "dodging through patterns of slow bullets", "only a tiny dot on my ship can be hit", "you score for nearly getting hit".
- **Bullet heaven** (Survivors-like, Vampire Survivors-like, Reverse bullet hell, Horde survival): You only move. Your weapons fire by themselves at an endless swarm, you collect the gems they drop, and each level offers a choice of upgrade. It promises to turn a weak character into a screen-filling storm in minutes. Described as: "the game shoots for you and you only move", "a game like Vampire Survivors", "hundreds of enemies and you melt them all", "picking one of three upgrades when you level up".
- **Fighting game** (Fighter, Versus fighter): Two characters, one screen, health bars and rounds. It promises a conversation between two people, conducted in punches, where you learn to read your opponent as much as your own buttons. Described as: "two characters fighting one on one", "a game like Street Fighter", "knowing how many frames a move takes", "you learn to read what the other player will do".
- **Rhythm game** (Music game, Rhythm action): Press in time with the music, and you are judged by how close you were to the beat. It promises the feeling of playing the music yourself, even if you cannot play anything. Described as: "pressing buttons in time with the music", "notes scroll down and you hit them on the beat", "a game like Guitar Hero", "it says early or late when I press".
- **Puzzle game** (Puzzler, Logic game): A game whose challenge is working something out, not doing it quickly. It promises the moment when the answer arrives and you feel clever, and that feeling is yours, because you got there. Described as: "a game about working out the answer", "the moment when you suddenly understand the solution", "I need to think, not react", "pushing crates into place".
- **Match-3** (Match three, Tile matching, Swap puzzle): Swap two neighbouring pieces to line up three of a kind. They vanish, the pieces above fall, and new lines may form by themselves. It promises small and constant rewards, plus sudden lucky cascades. Described as: "swapping gems to make a line of three", "a game like Candy Crush", "the pieces fall and match by themselves", "chain reactions when things fall".
- **Stealth game** (Stealth action): You avoid being seen rather than fighting. Guards have vision and hearing that you learn and exploit. It promises the tension of being one mistake away, and the satisfaction of never being noticed at all. Described as: "sneaking past guards without being seen", "the guards have a cone of vision", "I got spotted and do not know why", "a game where you avoid fighting".
- **Roguelike** (Traditional roguelike): A turn-based dungeon crawl on a grid, generated anew each run, where death is permanent. It promises that you can never just memorise your way through: only what you have learned comes with you. Described as: "when you die you start again from the very beginning", "a new random dungeon every time", "the monsters only move when I move", "a game like Rogue or NetHack", "what is the Berlin Interpretation".
- **Roguelite** (Rogue-lite): Takes the runs and the permanent death of a roguelike, and adds something that stays: currency or unlocks that make the next run stronger. It promises that no attempt is wasted. Described as: "you die but you keep some upgrades", "each run makes you a bit stronger", "a game like Hades", "losing still feels like progress", "meta-progression between runs".
- **Soulslike** (Souls-like, Soulsborne): Slow, heavy third-person combat, where stamina limits every swing and enemies have long tells you must learn. Death drops what you were carrying where you fell. It promises that hard things can be beaten by paying attention. Described as: "hard combat where you learn the boss", "a game like Dark Souls", "you run back to get what you dropped when you died", "I ran out of stamina mid fight", "bonfires bring all the enemies back".
- **Immersive sim** (Immersive simulation, Imsim): A world built from systems that follow consistent rules, in which problems have many answers and none is written in by hand. It promises that if your idea should work, it will. Described as: "the game has lots of ways to solve the same problem", "I tried something weird and it just worked", "a game like Deus Ex or Dishonored", "the world follows its own rules".
- **JRPG** (Japanese role-playing game, Turn-based RPG, Console RPG): A party-based role-playing game in the line of Dragon Quest: a set story and cast, turn-based menu battles, and levels that you raise by fighting. It promises a long journey with people you grow fond of. Described as: "turn-based battles picked from a menu", "a game like Final Fantasy", "I need to grind levels before the boss", "a party of characters with a long story".
- **CRPG** (Computer role-playing game, Western RPG, Isometric RPG): A role-playing game in the tradition of pen and paper: you make a character from stats, and the rules, often with visible dice, decide how they do. It promises a story that answers who you chose to be. Described as: "the dice decide if my character can do it", "a game like Baldur's Gate", "I built a character and the story changes for them", "a stat lets me say something different in a conversation".
- **MMO** (MMORPG, Massively multiplayer online game): A persistent online world shared with thousands of players at once, which carries on when you log off. It promises a place, and a society, more than a story: other people are the content. Described as: "a huge online world full of other players", "a game like World of Warcraft", "the world keeps going when I log off", "I need a guild to beat this raid".
- **4X** (Civ-like, Explore, expand, exploit, exterminate): Empire-building strategy, usually turn-based, whose name means explore, expand, exploit and exterminate. It promises to take you from a single settler to a world power, and it keeps you up with "one more turn". Described as: "building an empire from one city", "just one more turn", "a game like Civilization", "exploring a map then taking over the world".
- **Real-time strategy** (RTS): Gather resources, build a base, train an army and destroy the enemy, all at once in a continuous clock. It promises to make you a general, and tests how many things you can do at the same time. Described as: "building a base and an army at the same time", "a game like StarCraft", "clicking as fast as you can to control everything", "do I build more workers or more soldiers".
- **MOBA** (Multiplayer online battle arena, ARTS, Dota-like): Two teams, usually of five, each control a single hero, while waves of computer-run minions march down lanes between the bases. It promises a long, deep team match in which you level up from nothing each game. Described as: "five players each controlling one hero", "a game like League of Legends or Dota", "trying to land the last hit on minions", "pushing lanes to destroy the enemy base".
- **Tower defence** (TD): Enemies walk from one side to the other, and you stop them by placing towers that fire on their own. You never touch the enemies. It promises the joy of watching a plan you made work. Described as: "placing towers to stop waves of enemies", "enemies walk along a path and the towers shoot them", "making enemies walk a longer route", "a game like Plants vs. Zombies".
- **City builder** (City sim, Management sim): You lay out roads, homes and work, and a simulated population decides whether to move in. There is usually no win screen. It promises a place of your own that visibly comes alive. Described as: "building a city with roads and houses", "a game like SimCity", "people move in if you have jobs and roads", "traffic keeps getting worse as the city grows".
- **Deckbuilder** (Deck-building game, Roguelike deckbuilder): You start with a small and weak deck of cards, and you improve it as you play, adding and removing cards between hands or fights. It promises the delight of watching a pile of cards become a machine. Described as: "a card game where your deck grows as you play", "a game like Slay the Spire", "I keep adding cards but drawing the wrong ones", "removing bad cards to make the deck better".
- **Auto-battler** (Auto chess, Autobattler): You buy units from a shop and place them, then the battle fights itself while you watch. It promises strategy without any need for fast hands: the whole game is what you did before the fight. Described as: "the units fight by themselves after you place them", "a game like Teamfight Tactics", "buying three of the same unit to upgrade it", "you just watch the fight happen".
- **Incremental game** (Idle game, Clicker): Numbers go up, you spend them to make the numbers go up faster, and it carries on while you are away. It promises steady and absurd growth, with nothing ever taken away. Described as: "the numbers just keep going up", "a game that plays itself while I am away", "a game like Cookie Clicker", "I reset everything to get a multiplier".
- **Sandbox** (Software toy, Creative mode): A game that gives you tools and rules but no set goal. It promises that the only limit is your idea, and what you make is why you play. Described as: "a game with no goal where you just make things", "you can do whatever you want", "a game like Minecraft in creative mode", "I just mess about with the physics".
- **Survival craft** (Survival game, Crafting survival): You arrive with nothing. Hunger and the dark keep draining you, so you gather, craft better tools, and build a shelter. It promises the slow satisfaction of turning a hostile place into your home. Described as: "gather wood and craft things to stay alive", "I have to eat and find shelter before night", "a game like Don't Starve or Valheim", "starting with nothing and building up a base".
- **Open world** (Free roam): One large continuous place you can cross as you wish, doing things in nearly any order. It promises that if you can see it, you can go there. Described as: "you can go anywhere from the start", "if I can see that mountain I can walk there", "a huge map full of icons", "a game like Grand Theft Auto or Breath of the Wild".
- **Extraction shooter** (Extraction game, Tarkov-like): You enter a dangerous map with your gear, grab what you can, and must reach an exit alive. If you die, you lose it all. It promises a fear that no other shooter gives you: having something to lose. Described as: "you lose everything if you die before you get out", "a game like Escape from Tarkov", "do I grab one more thing or leave now", "looting then running for the exit".
- **Battle royale** (BR, Last man standing): Dozens of players land on a map with nothing, scavenge weapons, and fight until only one remains, while a shrinking safe zone forces them together. It promises that this match, you might be the one. Described as: "last one standing out of a hundred players", "the circle keeps shrinking and forces everyone together", "a game like Fortnite or PUBG", "you land with nothing and look for a gun".
- **Walking simulator** (Walking sim, Environmental narrative game, First-person exploration game): You walk through a place and piece together a story from what you find. You cannot fail, and there is little else to do. It promises the attention you would give to a good film, in a place you can stand inside. Described as: "all you do is walk around and find out a story", "there is no way to lose", "a game like Gone Home or Firewatch", "reading letters left in an empty house".
- **Visual novel** (VN, Dating sim (a popular kind), Sound novel): A story told in text, over character portraits and backgrounds, with occasional choices that send it down different branches. It promises the depth of a novel, and the sense that you changed how it ended. Described as: "a game that is mostly reading with pictures of characters", "picking choices to get different endings", "a dating game with character portraits", "clicking through dialogue with story branches".
- **Gacha game** (Gacha, Hero collector, Character collector): A game whose loop is earning currency through chores and spending it on random draws for characters. The name comes from gachapon, the Japanese capsule-toy machines. It promises the thrill of a rare pull, and a roster to show for it. Described as: "spending currency to pull random characters", "a game like Genshin Impact", "I got a rare one after 80 pulls", "a banner with limited characters", "the game guarantees one after a certain number of pulls".

## Together

- **Netcode** (Network code, Online code, Multiplayer architecture): The code and the rules that keep players on different machines in the same game, when no two of them can ever see the same moment. Described as: "the game plays fine offline but feels terrible online", "how do online games keep everyone in sync", "what makes one online game feel better than another", "the two players see different things".
- **Latency** (Ping, Lag, Round-trip time, RTT): How long data takes to travel between machines. Ping is the time there and back, in milliseconds, and part of it is simply the distance and the speed of light in glass. Described as: "the game is lagging", "there is a delay between me and the other players", "what does my ping mean", "playing with someone on the other side of the world feels slow", "high ping".
- **Jitter** (Packet delay variation, Unstable ping): How much the delay changes from one packet to the next. Packets sent on a steady beat arrive unevenly, and some overtake each other on the way. Described as: "my ping keeps jumping around", "the game stutters even though my ping is low", "other players move in fits and starts", "it is fine and then it isn't".
- **Packet loss** (Dropped packets, Loss): Some of what you send simply never arrives. Each game has to choose: ignore it, wait for it to be sent again, or send things in a way that makes it not matter. Described as: "the game freezes and then everything jumps", "I shot and nothing happened", "teleporting players", "the connection is dropping bits", "rubber banding on bad wifi".
- **Tick rate** (Tickrate, Server tick, Update rate, Hertz): How many times a second the server works out what has happened. Anything that reaches it between ticks has to wait for the next one. Described as: "I hit them but the game did not count it", "how often the server updates", "why 128 tick servers are better", "shots register late", "players seem to teleport a little".
- **Server authoritative** (Authoritative server, Dedicated server, Client-server): One machine, the server, decides what really happened. Players' machines send only what was pressed and show what they are told. Described as: "stopping players from hacking their position", "who decides what really happened", "can a client be trusted", "cheaters teleporting around", "dedicated servers".
- **Peer to peer** (P2P, Mesh): Players' machines talk straight to each other, with no server in the middle. Some designs have one player's machine act as host instead, so the others connect to it. Described as: "no servers, players connect directly", "one of the players is hosting", "the host left and the game ended", "host advantage", "playing without a dedicated server".
- **Lockstep** (Deterministic lockstep, Synchronous simulation): Every machine runs the entire game itself, and only orders cross the wire. Nobody moves on to the next turn until they have everyone's orders for it. Described as: "the whole game slows down because one player has bad internet", "how can a strategy game send thousands of units online", "waiting for player 3", "only sending the commands, not the positions".
- **Desync** (Out of sync, Determinism bug, Divergence): Machines running the same game stop agreeing about it. In a game that sends only inputs, one tiny difference grows until the players are in two different matches. Described as: "we were playing and then saw completely different things", "out of sync error", "the replay did not match what happened", "my unit died on my screen but not on theirs".
- **Delay-based netcode** (Input delay netcode, Frame delay): Hold your own inputs back for a few frames, so that the other machine's inputs for the same frame have time to arrive. If they still have not, freeze until they do. Described as: "the controls feel sluggish online but fine offline", "the online freezes and stutters", "my character responds late when I play someone far away", "input delay online".
- **Rollback** (Rollback netcode, GGPO, Rollback networking): Your own inputs happen at once, and the game guesses that the other player is still doing what they were doing. When their real input arrives and differs, it reloads a saved state and quickly replays every frame since. Described as: "the opponent teleported a bit but the controls felt perfect", "online feels like offline", "I got hit by a move that never seemed to start", "the game guesses what the other player will do", "why fighting game players want this".
- **Client-side prediction** (Prediction, Input prediction, Local prediction): With a server in charge, your own character moves the moment you press, on the assumption the server will agree. The server's answer comes a whole trip later. Described as: "the character moves as soon as I press, even with bad internet", "hiding the delay on your own character", "every action feels late online", "the game assumes your move worked".
- **Server reconciliation** (Rubber-banding (when it goes wrong), Correction, Replay): When a server update arrives, take its word for that moment in the past, then re-apply every input it has not yet seen. If you predicted correctly, nothing on screen moves. Described as: "my character keeps getting pulled backwards", "rubber banding", "I run forward and snap back to where I was", "the game corrects where I am", "teleported back".
- **Entity interpolation** (Interpolation, Lerp, Snapshot interpolation): Show other players slightly in the past, by drawing a smooth line between two updates you already have. They move evenly, and they are always a little older than they look. Described as: "other players glide smoothly instead of jumping", "what I see of other players is slightly old", "enemies are jittery and teleporty", "the other player moves in little hops".
- **Lag compensation** (Hit rewind, Favour the shooter, Backwards reconciliation): When a shot reaches the server, it rewinds everyone to where they were on the shooter's screen when they fired, and judges the hit there. Described as: "I got shot after I got behind the wall", "I aimed right at them and it hit", "the game favours the shooter", "peeker's advantage", "killed around a corner".
- **PvP and PvE** (Player versus player, Player versus environment): Whether you are playing against other people, or against the game. They change more than the opponent: a script can be learned, and a person learns you back. Described as: "fighting other players or fighting the computer", "the bot is predictable but people are not", "I do not want other players attacking me", "balancing for players and enemies".
- **Co-op** (Cooperative play, Co-operative, Team play): Players on the same side, against the game. Good co-op makes them need each other, not just share a screen or a map. Described as: "playing together on the same team", "I have to help my friend or we both lose", "picking up a downed teammate", "a game you need two people for".
- **Split screen** (Couch co-op, Local multiplayer, Shared screen): Players sit in one room, on one machine. Either they each get a slice of the television, or they share one view that has to keep all of them in it. Described as: "playing together on one TV", "we share the same screen", "the camera has to keep both of us in view", "the screen is cut in half", "couch multiplayer".
- **Asymmetric multiplayer** (One versus many, 1v4, Asymmetric PvP): The two sides play by different rules, with different abilities and different goals, such as one strong hunter against a team of weak survivors. Described as: "one player against a whole team", "each side plays a totally different game", "the monster is controlled by a person", "hide and seek style multiplayer".
- **Emotes** (Limited communication, Ping system, Quick chat, Pings): Giving players a small, fixed way to communicate: a wave, a canned phrase, a mark on the map, a single note. You can say only what the designers let you say. Described as: "communicating without chat", "pointing out something to a teammate", "the game only lets me wave or say a fixed phrase", "one button makes my character sing", "pinging an enemy".
- **Griefing and toxicity** (Griefer, Griefing, Toxicity, Trolling, Harassment, Toxic players): Griefing is using the game's own rules to spoil it for others, such as blocking a door or killing a teammate. Toxicity is abuse aimed at other people, usually in chat. Described as: "someone is ruining the game on purpose", "a teammate blocking me on purpose", "people being abusive in chat", "a toxic community", "killing their own teammates for fun".
- **Spectating** (Spectator mode, Observer mode, Stream delay, Stream sniping): Letting people watch a match in progress, usually from a free camera with information that the players do not have. Most such feeds run on a delay. Described as: "watching other people play live", "someone was watching my stream to find me", "stream sniping", "the stream is behind the real game", "esports camera".
- **Matchmaking** (Matchmaker, Queue, SBMM, Skill-based matchmaking): The system that picks who plays whom, trading how long you wait against how fair the game will be, and how good the connection is. Described as: "the game finds opponents for me", "it takes forever to find a match", "I keep getting matched with people way better than me", "dead game with long queues".
- **Elo and MMR** (Elo rating, MMR, Matchmaking rating, Skill rating, TrueSkill, Glicko): A number estimating skill. Elo compares your rating with your opponent's to work out how likely you were to win, then moves both by how surprised it was. MMR is the same kind of number in a game. Described as: "what is my skill number", "how does the game know how good I am", "I beat someone better and got loads of points", "a hidden number that decides who I play".
- **Ranked play** (Ranked, Competitive mode, Ladder, Tiers, Seasons, Rank inflation): A separate mode in which matches count, showing your standing as a named rank, such as Gold or Diamond. Those ranks are usually lines drawn across a rating, with a few extra rules. Described as: "climbing the ladder", "everyone is Diamond now, it means nothing", "my rank went up but I am not getting better", "seasons and rank resets", "a mode where matches count".
- **Smurfing** (Smurf, Alt account, Boosting (its cousin)): A skilled player on a new account, so they get matched with beginners. The system is doing exactly what it should, and it takes many one-sided games to find out. Described as: "beginners keep getting destroyed by experts", "someone with a new account is far too good", "a pro playing on a low-level account", "my first matches were against people who clearly were not new".
- **Anti-cheat** (Cheat detection, Kernel anti-cheat, VAC, Bans, Ban wave): Everything done to find and stop cheaters: software that looks for cheats on your machine, statistics on the server, and other players reviewing suspicious matches. Described as: "someone is obviously hacking", "aimbot", "the game banned me by mistake", "how do they catch cheaters", "why was he not banned sooner".

## The machine

- **Game engine** (Engine): The reusable software under a game: the parts that draw, play sound, read input, simulate physics and load files. The game itself is the rules and content built on top. Described as: "the software that games are built with", "Unity or Unreal or Godot", "what actually runs the game underneath", "do I have to code everything from scratch".
- **Game loop** (Main loop, Update loop): The circle at the centre of every game: read input, update the world, draw the picture, then do it again, usually dozens of times a second. One turn of it makes one frame. Described as: "the code that runs over and over while the game plays", "what happens every frame", "how does the game keep going when I do nothing", "why does my press take a moment to register".
- **Frame budget** (Frame time, 16.7 ms, Performance budget): The time one turn of the loop is allowed to take. At 60 frames a second that is 16.7 milliseconds, shared between everything: game logic, physics, AI, animation and drawing. Described as: "the game slows down when a lot is happening", "how long does one frame get", "drops from 60 to 30", "what is using up all the time", "the game stutters during explosions".
- **Delta time** (dt, Frame-rate independence, Time step): The time the last frame took. Multiply every movement by it, and a character covers the same ground per second however fast the machine runs. Described as: "the game runs faster on a better computer", "everything is in slow motion when the frame rate drops", "the speed changes with the frame rate", "game plays too fast on a high refresh monitor".
- **Fixed timestep** (Fixed update, Accumulator, Physics tick): Frames vary, so bank the time they take, and spend it on game logic in equal slices such as a 120th of a second. The picture can run at any rate while the rules always step the same. Described as: "jump height changes with frame rate", "physics behaves differently on different computers", "replays go out of sync", "how do I make the simulation consistent".
- **Collision detection** (Broad phase, Narrow phase, Spatial partitioning, AABB): Working out which things are touching. Done in two passes: a broad phase that quickly throws out everything that is nowhere near, and a narrow phase that does the exact test on what is left. Described as: "how does the game know two things touched", "the game slows down with lots of objects on screen", "checking every object against every other", "hitboxes and overlaps".
- **Tunnelling** (Bullet through paper, Clipping through walls): A fast object moves so far in one physics step that it starts on one side of a wall and ends on the other, and the game never sees them touch. Collision was only checked at the two ends. Described as: "the bullet went straight through the wall", "I fell through the floor", "fast things pass through thin things", "it worked until the frame rate dropped".
- **Physics engine** (Rigid body simulation, Solver, Havok, Box2D, PhysX): The part of an engine that moves things under forces and keeps them from passing through each other. It solves joints and contacts approximately, by nudging them in several passes each step. Described as: "objects that fall and stack and knock over", "ragdolls", "wobbly bridge that stretches", "things exploding when they touch", "realistic crates and barrels".
- **Raycast** (Ray test, Line trace, Hitscan (for weapons)): Asking what a straight line from here in that direction hits first, and how far away it is. It is the most common question in a game engine. Described as: "checking whether one thing can see another", "how does a gun know what it hit", "firing an invisible line", "is there ground under the character", "hitscan weapon".
- **Tween** (Easing, In-betweening, Interpolation curve): Moving a value from A to B over a set time along a curve, so you only state the start, the end and the feel. The word comes from animators drawing the frames in between. Described as: "smooth movement from one place to another", "the menu slides and slows down at the end", "make it bounce into place", "animation curves", "stuff moves too robotically".
- **Entity component system** (ECS, Data-oriented design): A way of organising a game. An entity is only an id, components are plain data attached to it, and systems are loops that run over everything holding the components they care about. Described as: "how do I organise all the game objects", "inheritance is getting out of hand", "I want to mix and match abilities", "a thing that is both an enemy and a door", "thousands of objects run slowly".
- **Scripting** (Scripting language, Gameplay scripting, Lua): Writing game behaviour in a simpler language that the engine reads and runs, while the fast, difficult parts stay in the engine. Described as: "changing behaviour without recompiling", "designers want to edit things themselves", "a simple language inside the game", "modding with text files", "Lua in games".
- **Hot reload** (Live coding, Hot swap): Changing code or data while the game keeps running, so the new version takes effect without restarting or losing your place. Described as: "change the code without restarting the game", "I have to replay the whole level to test one thing", "see my changes instantly", "tweak values while it is running".
- **Serialisation** (Saving state, Save data, Marshalling): Turning a live game's state into a flat stream of bytes that can go in a file or over a network, and back again. A save file is serialisation, and so is a network message. Described as: "how does the game save everything", "my save file is broken after an update", "after loading a save something is wrong", "sending game state over the network", "turning objects into data".
- **Object pooling** (Object pool, Free list, Garbage collection spikes): Keeping a stock of finished objects, such as bullets, and reusing them rather than creating new ones and throwing old ones away. Described as: "the game hitches every few seconds", "stutter when lots of bullets are firing", "reuse objects instead of creating new ones", "garbage collector pauses", "bullet from last time has the wrong colour".
- **State machine** (Finite state machine, FSM): A thing is in exactly one of a list of states, and a table says which event moves it to which state. An enemy might have Patrol, Chase and Flee, joined by events like "saw the player". Described as: "the enemy switches between behaviours", "the character can only do one thing at a time", "it attacked while it was already dead", "patrol then chase then attack", "too many if statements for what the character is doing".
- **Behaviour tree** (BT, Selector and sequence): AI written as a tree of tests and actions, walked from the top. A selector tries its children until one works; a sequence runs them until one fails. So the top is the most urgent. Described as: "the guard checks several things in order", "enemy AI that has priorities", "state machine got too tangled", "if it can see you it chases, otherwise it patrols", "node graph for enemy AI".
- **Utility AI** (Utility system, Needs-based AI, Scoring AI): The character gives every action it could take a score based on the situation, and does the one with the highest. How hungry am I, how far is the food, how much would it help. Described as: "the character decides based on what it needs most", "give each action a score", "behaviour like The Sims", "hunger and sleep and fun meters", "AI feels more alive and less scripted".
- **Goal-oriented action planning** (GOAP, AI planner): You give the character goals and a list of actions, each with what it needs and what it causes. A search then finds the cheapest chain of actions that reaches the goal. Described as: "the enemy figures out how to do something by itself", "AI that makes a plan", "if the door is locked it goes for the key", "enemies adapt when I remove their options".
- **Pathfinding** (A*, A star, Dijkstra's algorithm): Finding a route through a map. A* is the standard: always explore the most promising spot, judged by distance so far plus a guess at what is left, which finds a shortest route quickly. Described as: "how do enemies find their way to me", "the character walks into walls", "finding the shortest route on the map", "units get stuck on corners", "A star".
- **Navigation mesh** (Navmesh, Funnel algorithm): A set of flat polygons covering every place a character can walk. Search runs over the polygons rather than thousands of squares, and the route is then pulled tight round corners. Described as: "the walkable area of the level", "AI can't find its way round the furniture", "blue floor overlay in the engine editor", "paths look robotic and zigzag", "characters hug the walls".
- **Steering and flocking** (Boids, Steering behaviours, Separation, alignment, cohesion): Each creature follows simple local rules for its next movement. Craig Reynolds showed in 1987 that three are enough for a flock: keep apart, match your neighbours' heading, drift to their centre. Described as: "a group of birds or fish moving together", "enemies swarm without bumping into each other", "crowd movement", "no leader but they all move as one", "units stop overlapping each other".
- **AI director** (Director, Dramatic pacing, Adaptive pacing): A system above the enemies that watches how the players are doing, and decides when and where threats appear, to make the tension rise and fall. Described as: "the game gives you a break after a big fight", "no two playthroughs have the same enemies", "the game senses when I am overwhelmed", "peaks and quiet moments", "zombies arrive at just the right time".
- **Seed** (Random seed, World seed, Pseudo-random number generator): The one number a random generator starts from. Computers fake randomness with maths, so the same seed always gives the same sequence, and so the same world. Described as: "typing a code to get the same world", "share a map as a number", "daily challenge everyone plays the same", "the same random results every time", "reproducing a bug in a random level".
- **Procedural generation** (Procgen, PCG, Roguelike levels): Content made by an algorithm rather than by hand, at build time or as you play. The craft is in the rules around the randomness, since pure randomness rarely gives you a good level. Described as: "different level every time", "levels made by the computer", "endless worlds", "the game made a level that was impossible", "randomly generated dungeon".
- **Perlin noise** (Gradient noise, Fractal noise, Octaves, fBm): Random numbers that change smoothly, made by Ken Perlin. Add several layers, called octaves, each twice as fine and half as strong, and you get something that looks like hills and rock. Described as: "natural looking random terrain", "smooth random hills", "clouds and marble textures", "octaves of noise", "my random map looks like static".
- **Wave function collapse** (WFC, Model synthesis): Fill a grid with tiles that have rules about what may sit next to them. Each cell starts as anything; pick the most certain, decide it, and let the rules narrow its neighbours. Repeat. Described as: "tiles that automatically fit together", "generate a map from a set of rules about neighbours", "how does Townscaper work", "the algorithm where the map fills in like sudoku".
- **Shader** (Fragment shader, Pixel shader, Vertex shader, GLSL, HLSL): A small program that runs on the graphics card, usually once for every pixel or corner of a model, in parallel. It decides position and colour, and that decides how everything looks. Described as: "code that controls how things look", "the outline and cartoon look", "how do games make water or glowing effects", "everything looks different with one effect", "retro dithered look".
- **Draw call** (Batching, Instancing, Sprite atlas): One request from the game to the graphics card to draw a batch of triangles. Each one costs CPU time for setting things up, whatever the size of the thing being drawn. Described as: "the game is slow but there is not much on screen", "lots of small objects drop the frame rate", "how do I combine sprites into one", "CPU is the bottleneck, not the graphics card".
- **Level of detail** (LOD, Pop-in, Nanite): Using a simpler version of a model the further away it is. Done well, you never notice. Done badly, you see things change shape as you approach, which is called pop-in. Described as: "things change shape when you get closer", "distant objects look blocky", "textures and trees pop in", "how do open world games draw so much", "simpler models far away".
- **Culling** (Frustum culling, Occlusion culling, Potentially visible set): Not drawing what you can't see. Frustum culling skips things outside the camera's view. Occlusion culling skips things hidden behind something else, which is harder to work out. Described as: "the game doesn't draw what is behind you", "objects disappear at the edge of the screen", "things vanish when you turn the camera quickly", "walls should hide what is behind them".
- **Dynamic resolution** (Dynamic resolution scaling, DRS, Resolution scaling): The game watches its own frame time and lowers the number of pixels it renders when things get heavy, then scales the picture up to fill the screen. Described as: "the picture gets blurry in big fights", "the game lowers the resolution to keep the frame rate", "trading sharpness for smoothness", "console game looks softer during explosions".

## Making it

- **Graybox** (Blockout, Whitebox, Greybox): A playable version of a level or game made only of plain untextured shapes. The hero of this site, Noun, begins as one: a square with the physics values the code calls GRAYBOX. Described as: "the level is just grey boxes", "testing a level before it has any art", "placeholder blocks instead of real scenery", "building the rough shape of a level first".
- **Prototype** (Proof of concept): A quick, throwaway version built to answer one question, such as "is this fun?" or "can the engine do this?". You expect to bin it. Described as: "a rough test version of an idea", "trying something out before committing to it", "ugly version just to see if it works", "a throwaway build".
- **Find the fun** (Following the fun): Prototyping until you discover what is actually enjoyable in an idea, and then building towards that rather than towards the original plan. Described as: "the bug turned out to be the best part", "the game changed direction because something was unexpectedly fun", "working out what is actually enjoyable", "the original idea was not the fun part".
- **Game jam** (Jam): An event where people make a whole small game in a fixed short time, often 48 hours, usually to a theme. Ludum Dare has run since 2002 and the Global Game Jam since 2009. Described as: "making a whole game in one weekend", "a 48-hour game making event", "a competition to make a game fast around a theme", "rushing out a tiny game with friends".
- **Game design document** (GDD, Design doc): The written description of what a game is and how it works: its rules, systems, content and goals. On a good team it is a living reference that gets changed, not a contract. Described as: "the document that says how the whole game works", "where all the design decisions are written down", "the big game plan document", "nobody reads our design doc".
- **One-pager** (One-page design, Pitch sheet): A single page that says what a game or a system is: what the player does, who it is for and why it is exciting. If it won't fit on one page, you probably haven't decided yet. Described as: "the whole idea on a single sheet of paper", "a short summary of the game to pitch it", "explaining the game in one page", "a design doc people will actually read".
- **Vertical slice** (Slice): A short part of the game finished to final quality in every discipline at once: art, sound, code, design and interface. It is one thin slice through the whole cake. Described as: "one finished level that shows what the whole game will be like", "a polished demo for the publisher", "making a small part to final quality first", "how much does one minute of the real game cost".
- **Pre-production** (Preprod): The phase in which a small team works out what the game is and how to make it, with prototypes, tools and plans, before a large team is hired to build it. Described as: "the planning phase before the real work starts", "working out what the game is before hiring everyone", "a small team figuring things out first", "we started building before we knew what it was".
- **Production** (Full production): The main phase of making the game, when the design is settled and the full team builds the levels, art, code and sound. It is mostly a matter of keeping work flowing. Described as: "the main part of making the game", "everyone is building levels and art now", "work is piling up waiting for one department", "the phase after the planning is done".
- **Milestone** (Deliverable, Milestone build): An agreed date when a defined piece of work must be delivered and checked. With a publisher, passing one is commonly how the next part of the money gets paid. Described as: "the publisher pays when we hit a checkpoint", "an agreed checkpoint in the schedule", "we have to show a build by a set date", "a date with a definition of done".
- **Alpha** (Feature complete, Feature freeze): The point when every feature is in the game and can be played, however buggy and however ugly. After it, the rule is that no new features go in. Each studio draws this line slightly differently. Described as: "all the features are in but it is buggy", "no more new features from now on", "the game can be played from start to end but is rough", "feature freeze".
- **Beta** (Content complete, Open beta, Closed beta): The stage when all features and content are in and the work is finishing and fixing. A public beta opens this to outside players, usually to test servers and balance. Described as: "testing the game with the public before release", "the servers need a stress test", "everything is in and we are only fixing bugs now", "players can try it early but it is unfinished".
- **Gold master** (Going gold, Release candidate, RTM): The final approved build, the one that goes to the disc plant or the storefront. "Going gold" is named after the gold master discs that used to be sent for pressing. Described as: "the game is finished and sent to be manufactured", "the final build is approved", "we went gold", "the version that goes on the disc".
- **Crunch** (Crunch time, Death march, Overtime): Long stretches of forced overtime to hit a date, sometimes for months and often unpaid. It is common in the games industry, it damages people, and it is usually the result of a planning failure. Described as: "everyone is working weekends to hit the date", "forced overtime before release", "100-hour weeks", "the team is burning out to ship the game".
- **Scope** (Project scope): How much game you are trying to make: how many features, levels, characters and hours. It is the one project variable you fully control, and beginners nearly always set it too high. Described as: "the game is too big for our team", "how much game can we actually make", "we are trying to do too much", "cut it down to something we can finish".
- **Scope creep** (Mission creep): The project slowly growing during development, through a long series of small additions that each seemed reasonable, without the deadline or the budget moving to match. Described as: "the project keeps getting bigger", "just one more small thing, again and again", "nobody decided this but now the game is twice the size", "the deadline slipped because of little additions".
- **Feature creep** (Featuritis, Kitchen sink design): The game collecting more and more features, because each sounded good, until they crowd each other out and the original idea is hard to find. Described as: "the game has too many systems", "we keep adding features because other games have them", "crafting and fishing in a game that does not need them", "too much stuff and no focus".
- **Kill your darlings** (Cutting): Cutting something you love because the game is better or more finishable without it. The advice comes from writing: Arthur Quiller-Couch told students to "murder your darlings" in a 1914 lecture. Described as: "cutting a feature you really love", "it took months but the game is better without it", "we should remove our favourite part", "nobody wants to admit the cool thing has to go".
- **Playtest** (User testing, Hallway test): Watching other people play your game to see what really happens. You say nothing and take notes, and you do not explain or help. Described as: "watching someone else play your game", "people could not find the door I thought was obvious", "testing whether players understand it", "I am too close to my own game to see it".
- **Think-aloud** (Think-aloud protocol): A playtest in which you ask players to say what they are thinking as they play. It comes from psychology and from usability research, where Clayton Lewis applied it at IBM in the early 1980s. Described as: "asking players to talk while they play", "I want to know why they went that way", "getting testers to say what they are thinking", "players had the wrong idea about something".
- **Telemetry** (Analytics, Game analytics, Instrumentation): Data the game records and sends back about what players do: where they quit, how long a level takes, which weapons they use. It should be disclosed and it should not identify people needlessly. Described as: "tracking what players do in the game", "how many people finished the first level", "data on where players quit", "the game sends statistics back to us".
- **Heatmap** (Death map, Kill map): A map of a level coloured by how often something happened at each spot: where players died, walked, stopped or looked. It is telemetry you can see at a glance. Described as: "a map of where everyone keeps dying", "seeing where players go on the level", "colouring the level by what happens there", "everyone dies at the same spot".
- **Bug triage** (Triage, Bug scrub): Deciding which bugs to fix first, and which never to fix, using how bad each one is (severity) and how often players meet it (frequency). Described as: "deciding which bugs to fix first", "we cannot fix them all before launch", "how bad is it and how many people will see it", "some bugs will never get fixed".
- **Technical debt** (Tech debt): The future cost of a quick fix or a messy shortcut in the code. Like a loan, it buys you speed now and charges interest on all later work until it is paid. Ward Cunningham coined the comparison in 1992. Described as: "the code is such a mess that every change takes ages", "a quick hack we will have to clean up later", "we need to rewrite this before adding anything", "things that used to take an hour now take a week".
- **QA** (Quality assurance, Game testing, Testing): The work of finding what is broken before players do, by testing every system, edge and combination on purpose and writing bugs up so they can be reproduced. It is skilled work and often underpaid. Described as: "testers trying to break the game", "finding bugs before release", "someone walks into every wall to check it", "how do we make sure nothing is broken".
- **Localisation** (L10n, Translation, Internationalisation, i18n): Adapting a game for other languages and places: translation, but also longer text, right-to-left reading, fonts, voice acting, date formats and culture. Internationalisation is the engineering that makes it possible. Described as: "translating the game into other languages", "German text does not fit in the button", "the menu needs to read right to left", "bad translation in a game".
- **Certification** (Cert, TRC, XR, Lotcheck, Submission): The check a console maker runs before a game can be released on its machine. Sony calls its list TRC, Microsoft XR and Nintendo Lotcheck. They test things like save handling, button names and what happens when a controller is unplugged. Described as: "the console maker has to approve the game", "our game failed the PlayStation checks", "rules for releasing on a console", "it got rejected because the button names were wrong".
- **Day-one patch** (Day-zero patch, Launch patch): An update that is ready when a game launches, holding the fixes made in the weeks after the final build went off to be manufactured or certified. Described as: "a big download on the day you buy the game", "the disc version is not the finished game", "fixes ready for launch day", "why does a new game need an update straight away".
- **Post-mortem** (Postmortem, Retrospective): A look back after a project, or a failure, at what went right, what went wrong and what to change next time. The aim is to fix how you work, and it is pointless if it becomes a search for someone to blame. Described as: "looking back on what went wrong with the project", "what did we learn from making this", "a review after the game ships", "five things that went right and five that went wrong".
- **Art bible** (Style guide, Visual bible): A shared document that sets how the game looks and how to get that look: palette, shapes, materials, proportions and line, with examples of what is right and wrong. Described as: "everyone draws in a different style", "the rules for how the game should look", "keeping the art consistent between artists", "a style guide for outside artists".

## Selling it

- **Premium** (Pay once, Buy to play, B2P): The player pays once, up front, and owns the whole game. It is the oldest model there is. Described as: "you just buy the game and that is it", "pay once and own it", "no microtransactions, one price", "how much should I charge for my game".
- **Free-to-play** (F2P, Freemium): The game costs nothing to download and earns money by selling things inside it. Most players never pay, so the few who do carry the rest. Described as: "the game is free but it keeps asking for money", "free download with a shop in it", "how do free games make money", "most people never pay".
- **Platform fee** (Store cut, Revenue share, Rev share, 30%): The share of each sale the store keeps. Steam's standard cut is 30%, falling to 25% and then 20% on revenue above set amounts. Described as: "how much does Steam take", "what do I actually keep from a sale", "the store takes a cut", "30 percent".
- **Store page** (Capsule art, Capsule, Key art, Steam page): The page where someone decides whether to buy or wishlist. Capsule art is its small banner image, which is what most people see first, in a list among others. Described as: "the little image for my game on Steam", "nobody clicks on my game", "what should the store page look like", "the thumbnail for the game".
- **The hook** (Elevator pitch, USP, Unique selling point): The one thing that makes someone who has never heard of your game want it, said in a sentence. It needs to be something they can imagine doing and have not seen before. Described as: "how do I describe my game in one sentence", "what makes my game different", "nobody understands what the game is", "elevator pitch".
- **Wishlist** (Wishlists, Wishlist count): A saved list of games a player wants on a store. When a game on it launches or goes on sale at 20% or more, Steam emails them. Described as: "people saving my game to buy later", "how do I get people to remember my game", "get an email when a game launches", "how many wishlists do I need".
- **Demo** (Free trial, Slice, Steam Next Fest demo): A free piece of your game for people to try. On Steam, Next Fest is an event where many games release demos at once for visitors to browse. Described as: "try before you buy", "should I release a free bit of the game", "a short free version", "Steam Next Fest".
- **Early access** (EA, Steam Early Access, Paid beta): Selling a game before it is finished, and updating it in public. Steam started its programme in March 2013. Described as: "selling the game before it is finished", "it is playable but not done", "players test it while you keep building", "paid beta".
- **Discounting** (Sale, Launch discount, Steam sale): Selling for less for a while to reach people who would not pay full price. Expect many of your copies to sell at a discount, and plan for it. Described as: "when should I put my game on sale", "how deep should a sale go", "everyone waits for the Steam sale", "why would I sell my game for less".
- **Publisher** (Advance, Recoup, Publishing deal): A company that pays for or markets your game in return for a share of the money. Often they pay an advance, and you get no share of sales until your share has paid it back, which is called recouping. Described as: "do I need a publisher", "they pay me money up front but take a share", "what does recoup mean", "someone offered to fund my game".
- **Streamability** (Watchable, Twitch-friendly, Clip-worthy): How much fun a game is to watch someone else play: whether it makes moments people would clip and share, and whether viewers can follow it. Described as: "the game looks fun to watch", "streamers made this game blow up", "funny clips of people failing", "watching someone play made me buy it".
- **Review bombing** (Review bomb, Off-topic reviews): A flood of negative user reviews in a short time, often about something other than the game itself: a policy, a statement, a store deal. Described as: "people flooding a game with bad reviews", "the score crashed overnight", "angry about something that is not even the game", "mostly negative all of a sudden".
- **DLC** (Downloadable content, Expansion, Add-on): Extra content sold after the base game. It can be a large expansion or a small item, and players judge the two very differently. Described as: "extra content you pay for after", "an expansion pack", "they cut this out to sell it later", "should I sell extra levels".
- **Cosmetics** (Skins, Vanity items, Hats): Paid items that change how you look and nothing about how you play. Described as: "skins that do not affect gameplay", "paying just to look cool", "buying a hat for my character", "does it give an advantage or is it just looks".
- **Pay-to-win** (P2W, Pay for advantage): Players can buy an advantage over other players. Money beats skill, at least some of the time. Described as: "you can buy your way to the top", "I lost to someone who paid", "real money gets you better gear", "the game is rigged for people who spend".
- **Premium currency** (Hard currency, Gems, Virtual currency, Paid currency): Money you buy with real money and then spend in the game, as gems or coins. It sits between your wallet and the price, on purpose. Described as: "I do not know how much this really costs", "buy gems to buy the thing", "I always have a few coins left over", "the pack sizes never match the prices".
- **Energy system** (Lives, Stamina, Timers, Wait or pay): You can only play so much before the game makes you wait, with a meter that refills over time or for money. Described as: "the game makes me wait to keep playing", "I ran out of lives", "come back in three hours or pay", "why can I not just keep playing".
- **Battle pass** (Season pass, Reward track): A track of rewards you unlock by playing during a season, usually with a free line and a paid one. Dota 2's 2013 Compendium was the forerunner, and Fortnite made it the norm from late 2017. Described as: "I paid for the pass and now I have to grind it", "levels of rewards that run out at the end of the season", "I am behind on the battle pass", "this game feels like a job".
- **Loot box** (Crate, Random item box, Surprise mechanics): A paid item with a random reward inside, so you pay for a chance at what you want. It runs on the same schedule that keeps people at slot machines, with a game wrapped around it. Described as: "paying for a random item", "you do not know what you are buying", "opening crates", "is this gambling".
- **Gacha** (Banner, Pulls, Wishes, Pity timer, Soft pity): A loot box system built into the core of a game: you pay for pulls on a banner to win characters at very low odds. The word comes from Japanese capsule-toy machines called gachapon. Described as: "pulling for a character", "how much does it really cost to get the character", "pity timer", "the banner ends soon and I have not got it", "lost the 50/50".
- **Whale** (High spender, Big spender, VIP, Dolphins and minnows): Trade slang for the small number of players who spend far more than anyone else. It comes from casinos, where it means a high roller. Described as: "the few players who spend thousands", "a tiny number of people pay for everyone", "who actually spends money on these games", "big spenders".
- **Live ops** (Live operations, Live service, Games as a service, GaaS): Running a game after launch as an ongoing service: events, new content, balance changes, seasons, all planned on a calendar. Described as: "the game keeps getting events and updates", "a game that never ends", "running the game after launch", "seasons and limited events".
- **Soft launch** (Beta market, Test market): Releasing a mobile or live game quietly in a few countries to measure how people behave and fix it before the big release. Described as: "releasing it in just one country first", "testing the game before the real launch", "how many players do I need to test with", "our numbers look bad but it is only a few hundred players".
- **Retention curve** (Day-1 retention, D1, D7, D30, Churn, Cohort retention): The share of players who come back after a given number of days, starting from those who first played on the same day. Day-1 retention is the share who return the next day. Churn is the opposite: those who leave. Described as: "how many players come back the next day", "everyone quits after the first day", "players leaving the game", "what is churn".
- **DAU and MAU** (Daily active users, Monthly active users, Stickiness, DAU/MAU): How many different people played on a given day, and in the last 30 days. Dividing the first by the second gives a rough idea of how often people come back. Described as: "how many people play each day", "monthly active users", "how many players does the game really have", "stickiness".
- **ARPU and ARPDAU** (Average revenue per user, Average revenue per daily active user, ARPPU): Total revenue divided by players, over a period. ARPDAU divides one day's revenue by that day's players. ARPPU counts paying players only. Described as: "how much money do we make per player", "average spend per player", "revenue per daily user", "what is ARPDAU".
- **Lifetime value** (LTV, LTV/CAC, Payback): The money you expect from a player over all the time they play. If it's more than you pay to acquire one, you can buy growth with advertising. Described as: "how much is a player worth", "can we afford to buy ads", "when do we get our ad money back", "LTV".