Bullet heaven
Also said as 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.
One control means anybody can play, and all the decisions move to the level-up screen. The swing from desperate to all-powerful inside one run is the whole appeal.
Say it
“Bullet heaven: movement only, weapons auto-fire, a level-up every 20 seconds at the start with a choice of three, and 500 enemies on screen by minute ten.”
Where you’ve seen it
Vampire Survivors, by Luca Galante under the name poncle, reached version 1.0 in 2022. A run lasts 30 minutes, at which point Death arrives to end it, and weapons combine into stronger forms if you picked the right pairs.
Not to be confused with twin-stick shooter
In a twin-stick shooter you aim, and your skill is in your hands. In a bullet heaven the aiming is done for you, and your skill is the build.