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📏 Geometric Size Illusion Lab

📏 Geometric Size Illusion Lab

Six classic length illusions — Müller-Lyer, Ponzo, Ebbinghaus, Delboeuf, vertical-horizontal and Jastrow — drawn live, with a strength slider, a measure-it overlay printing true pixel lengths and a bias self-test.

Choose an illusion
🧪 Self-test: match the left one

Drag the slider until the right-hand figure looks the same size as the left. Then reveal the answer — your error is printed as a percentage. Repeat a few times for an average bias.

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Everything here is drawn with plain canvas maths and runs offline. Illusion strength varies a lot between people and is not a measure of eyesight or intelligence.

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