Depth test
Four discs float above the dots. One of them floats a little nearer to you than the other three. Pick it with the arrow keys, or tap where it is.
Each right answer makes the next difference smaller, and each wrong one makes it bigger, until the test settles on the smallest step you can see. It takes about two minutes.
Your result
This browser can't draw the stereograms: they need web workers and OffscreenCanvas.
Look
How to see it
- Sit about an arm's length from the screen.
- Look at the two dots under the picture, then let your eyes relax as if you were looking at something far behind the screen. Each dot splits in two.
- Let the four dots drift until the middle pair overlaps and you see three. Hold the middle one, then let your gaze wander up into the picture.
- The shape firms up the longer you hold it. If it sinks into the page instead of standing out, your eyes are crossed: relax them the other way, or turn on Cross-eyed under Look.
Still nothing? Slide lays a copy of the picture over itself. Drag it sideways and the shape shows up where the copy stops matching.