Color Test — a free colour perception game in your browser

Every level puts a grid of identical tiles in front of you, except one of them isn't identical — it's a fraction lighter or darker. Tap the odd one and you move on to a bigger grid with a smaller difference. Miss it once and the run is over, so the level you reach is a fairly honest measure of how fine a shade difference you can still resolve.

Level 1 is a 2×2 with an obvious gap. Somewhere past level 13 the grid is 6×6 and the difference is a couple of points of lightness — at which point you stop looking and start letting the pattern come to you. Free, no download, works on any phone or desktop.

How to play

• Find the tile whose shade doesn't match the others and tap it.
• Each level the grid grows and the colour gap shrinks.
• One wrong tap ends the run — there are no lives, so don't guess.
• Your score is levels completed, and the missed tile is revealed at the end.

Why the odd tile "pops" — and then suddenly doesn't

At the easy levels you aren't really searching. The odd tile is found by what vision researchers call pre-attentive processing: a difference big enough to register across the whole visual field at once, before you consciously look anywhere. That's why level 3 feels instant no matter how many tiles are on screen — grid size barely costs you anything while the difference is large.

Then the difference drops below that threshold and the task changes completely. Now you're doing serial search, comparing tiles a few at a time, and every extra tile genuinely costs time. The jump in difficulty you feel around the middle of a run isn't the game getting unfair; it's your visual system switching strategies.

Two things genuinely help. First, compare neighbours, not memories — your eye is far better at judging two patches side by side than at recalling a shade from a second ago, so scan along edges rather than hopping around. Second, defocus slightly. Peripheral vision pools signal over a wider area, which is exactly what you want when the difference is small and spatial detail is irrelevant.

Worth saying plainly: this is a game, not a medical test. Your score depends heavily on your screen, its brightness, and the light in the room — the same eyes will score differently on an OLED phone at night and a dim laptop at noon. It cannot detect colour blindness, and it isn't designed to. If you have a real concern about your colour vision, that's a conversation for an optometrist, not a browser tab.

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• Stroop Test — The word says BLUE, the ink is red. Answer the ink. Ninety years of psychology says you'll hesitate.
• Memory Match — Sixteen cards, eight pairs, one clock. The classic pairs game, ranked on how fast you clear it.
• Number Rush — Find 1 to 25 in order, as fast as you can. Stare at the middle — your eyes are slower than you think.
• Times Tables — Sixty seconds of multiplication, starting easy. Every four right answers unlocks another table, up to the twelves.

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