Color Master

About this test

The human eye is far more sensitive to differences in brightness than to differences in pure hue, and the smallest perceptible change depends on the starting level: you catch a one per cent gap on a mid grey and do much worse in very dark or very light tones. That's the differential threshold, and this test drives it down level after level until you lose the thread.

Three outside factors matter enormously here, often more than your vision. The screen first: an eight-bit panel can only show 256 levels per channel, so the finest gaps in this test eventually become unrepresentable, and a TN panel viewed slightly off-axis shifts the colours at the edges. Then ambient light: a reflection or a lamp behind you adds a flat layer of luminance that crushes low contrast. Finally night mode or any blue-light filter, which skews the hue of the entire screen and makes some gaps invisible.

Important: this is not an eye exam and it detects nothing. It does not assess colour blindness, which is diagnosed with specific plates under controlled lighting, and a low score means nothing medically. It's a visual attention game where the grid grows as the gap shrinks, deliberately mixing perceptual fineness with the ability to scan an image.

How it works

Each level shows a grid of squares in the same colour, except one that is slightly lighter. You click it. Each success enlarges the grid and narrows the brightness gap; each mistake costs a life. Once three lives are gone the run ends and your score is the level you reached.