Which Cup?

a red ball goes under a brass cup. stay with it.

the shell game on green baize: follow the red ball through longer, faster shuffles and more cups, and when you lose it, see the crossing where it went

Your eyes can stay on one moving cup among identical ones, but not at any speed. When two cups that look the same pass each other quickly, your eyes decide which one came out where, and at speed that decision slips without your noticing: you follow the wrong cup, sure of it. Every cup is visible in every frame and the ball never changes cups. A miss draws the ball’s route and your cup’s, from the last time the two traded places.

Concepts: attention, perception.

An interactive you play with one thumb, on Wundr.