One tile differs in colour — tap it. The gap shrinks each round. At the end, see your colour-resolution report.
Each round's colour gap is not a naive HSL tweak — it's a fixed perceptual distance (ΔE) measured in OKLCH/OKLab space. Most games of this kind just nudge HSL lightness a few percent, which happens to make yellow bases about 3x harder than blue ones — which hue gets punished is an accident of the colour space. Fixing ΔE means the same round is the same distance on all six bases. The base hue and perturbation axis (hue/chroma/lightness) are drawn at random every round — spread by chance, not by a fixed rotation, so a few consecutive rounds can land on the same hue.
The six-sector wheel shows your discrimination threshold per hue sector (red-orange, yellow, green, cyan, blue, violet) — the ΔE at which your success rate falls to half. Lower is sharper. It is fitted from every judgement you have made across runs (hue, actual ΔE, right or wrong), not from a single run: with one life every round before the last is correct by construction, so a single run's numbers only reflect which round you died on, not who you are. That is why a new player sees an empty wheel and it fills in over several runs. If you have never missed in a sector we can only say "better than ΔE X" rather than name a threshold; hatched sectors have not accumulated enough yet. Screen calibration and ambient light are unknown, so the number is meaningful only against your own history, never against someone else's.
Displayed ΔE = OKLab Euclidean distance × 100 — an internally consistent, auditable difficulty scale. It is not CIEDE2000 and we make no clinical precision claim. Discrimination here happens on an uncalibrated consumer screen at unknown brightness and ambient light; what you measure is "your ability on this screen in this room right now," not a physiological eye value. This is not a colour-vision screening and cannot substitute for a clinician's examination. On colour-vision differences, plainly: axis and base hue are drawn at random each round, and the lightness axis (about a third of rounds) is essentially unaffected by red-green differences. But a hue-axis round on the yellow or blue base moves along the red-green direction almost exactly, so those rounds are genuinely harder if you have a red-green deficiency. This game is not fully fair in that respect. The "by kind of difference" rows in the report are the readout that means something for you — the six hue sectors on the wheel pool all three kinds together.
Quick guide
Compact below-tool notes that help first-run users and repeated visitors move faster without changing the main interface.
Chinese search: 找不同顏色、色塊遊戲、色感測試、眼力測試、分辨顏色遊戲、一格之差、色相辨色、色覺遊戲
How to use
Examples
FAQ
No. This is a rough personal measurement on an uncalibrated screen at unknown brightness and ambient light — it's a game. Real colour-vision screening requires a clinician, not a web page.
Difficulty is a perceptual colour difference (ΔE) in OKLCH/OKLab space, not a raw HSL lightness tweak. Most games of this kind nudge lightness a few percent, which happens to make yellow bases roughly 3x harder than blue ones — which hue gets punished is an accident of the colour space. Fixing ΔE means round N is the same distance on all six bases.
Every judgement you have made across runs (hue sector, the ΔE actually achieved, right or wrong) is accumulated, and each sector is fitted for the ΔE at which your success rate falls to half. Why across runs? With one life, every round before the last is correct by construction, so a single run's numbers only reflect which round you died on — they cannot measure you. A sector you have never missed is reported as "better than ΔE X" rather than given a threshold; sectors without enough data stay hatched instead of pretending.
Displayed ΔE = OKLab Euclidean distance × 100. It's an internally consistent, auditable difficulty scale, not CIEDE2000. We make no clinical precision claim.
Partly, and it is better to say so plainly. The axis and base hue are drawn at random each round, and the lightness axis — about a third of rounds — is essentially unaffected by red-green differences. But a hue-axis round on the yellow or blue base moves almost exactly along the red-green direction, so those rounds are genuinely harder with a red-green deficiency. The game is not fully fair in that respect. The "by kind of difference" rows in the report (hue / chroma / lightness) are the readout that means something for you; the six hue sectors on the wheel pool all three kinds together.