Value structure
Also said as 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.
The eye reads value before hue, so a picture with weak values turns to mud however lovely the colours are. It is also what survives for players with colour blindness.
Say it
“Do a squint test on this level. Keep three value groups: a dark foreground for the play space, a mid-grey background, and bright only where the player should look. Check it in greyscale before adding colour.”
Where you’ve seen it
Limbo has no colour at all, so everything it tells you, from depth to danger, has to be carried by value.
Not to be confused with saturation
Saturation is how strong a colour is. Value is how light or dark it is. Two very different hues can have the same value and melt together in grey.