Sixty seconds to find the one tile that is a slightly different colour

What gets harder as you level up

Two things at once. The grid grows from 2×2 up to 9×9, so there is more to scan, and the brightness gap between the odd tile and the rest keeps shrinking. Hue and saturation stay identical — only lightness differs — so what this really measures is how fine a brightness difference your eyes and your screen can resolve together.

How to actually find it faster

Reading tile by tile runs out the clock. Defocus slightly and take in the whole grid at once — the odd tile surfaces as a smudge. Peripheral vision is more sensitive to luminance differences than your central vision, so not staring directly is genuinely the better strategy. Turning screen brightness up and auto-brightness off helps as much as any technique.

A low score does not mean colour blindness

This is a brightness discrimination task, not a hue one, so red-green colour deficiency barely affects it. The real limiter is usually your display. A cheap TN panel, a dimmed screen, or night mode / blue light filter crushes the finest steps before your eyes ever get them. The same person will score noticeably differently on an OLED phone and a budget laptop.

Age and contrast sensitivity

Luminance discrimination peaks in the mid-twenties and declines gently after that, largely because the lens yellows with age and lets through less light. Someone in their forties is effectively seeing a slightly dimmer screen than someone in their twenties — which is also why anyone scores better in a bright room.

How a round works

Grid size and colour gap by level

The grid is 2 + (level − 1) ÷ 2 tiles per side, rounded down, capped at 9. That gives 2×2 at levels 1–2, 3×3 at 3–4, 4×4 at 5–6, 5×5 at 7–8, 6×6 at 9–10, 7×7 at 11–12, 8×8 at 13–14 and a full 9×9 (81 tiles) from level 15 on. Each round picks a random hue, a saturation between 55 and 90 percent and a base lightness between 38 and 68 percent; only the odd tile is shifted lighter or darker (a coin flip) by (40 − level × 1.6) ÷ 2 lightness points. Level 1 is about 19 points apart and obvious to anyone; level 10 is 12 points, level 20 is 4, and from level 23 the gap sits at its floor of 2 points. Passing 40 means picking a 2 percent lightness difference out of 81 tiles in roughly a second each.

Grades

The percentile next to each grade is a fixed label attached to that band, not a live statistic. For your real standing, check the global leaderboard on the title screen.

Leaderboard and records

The global leaderboard is the top 10 by tiles found, entered with a nickname of up to 12 characters; a round with zero finds cannot be submitted. Your personal best is stored in the browser and shown on the title screen. The share link carries your count and grade, so a friend who opens it sees your number as the score to beat before playing. Leaving the play screen mid-round stops the clock and ends that round.

Is there any way to gain time?

No. The 60 seconds are fixed and correct taps add nothing back. Since only wrong taps cost time, 3 seconds each, waiting half a second longer to be sure beats guessing.

What does highest level mean?

It is the level you reached in that round, which is always your count plus one. The level only rises on a correct tap and never falls on a wrong one, so it restates your score in terms of grid size and colour gap rather than adding a separate measure.

Can I use this as a colour blindness test?

No. This measures how fine a lightness difference you can resolve, which is a different ability from telling hues apart. To check for colour vision deficiency, try the Color Vision Test, which uses Ishihara-style numbers hidden in dots.

Does a bigger screen help?

The grid scales with the viewport up to 520 pixels, so tiles are larger on a tablet or desktop. Screen size matters less than panel brightness and lightness rendering, though: on the same device, night mode off, auto-brightness off and brightness turned up is the best condition you can give yourself.

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