Mole

tap the mole before it ducks.

a whack-a-mole cabinet whose speed is a staircase that settles at your reaction time

Every catch makes the next mole stay up a little shorter, and every one that gets away makes the next stay up longer. So the moles walk to the speed where you catch about three in five, and the up-time they settle at is how long your hand needs to see a mole and reach it.

Concepts: timing, attention, perception, feedback-loops.

An interactive you play with one thumb, on Wundr.