Chopsticks

the egg is the hard one.

thirty seconds at a ramen counter: hold to grip, drag to the spoon, and do not squeeze the egg

A thing held between two chopsticks stays put only inside a band of grip. Below the band it slides out the moment you move; above it the soft ones shoot out sideways, which is what a soft-boiled egg does to everyone. The width of that band is a fact about the thing -- a slice of pork forgives nearly anything, a square of nori slides at a touch, and the egg has the narrowest band on the table. Here the grip is how long you have held, so the whole game is how long you dare wait before you move, and how fast you then go.

Concepts: friction, physics.

An interactive you play with one thumb, on Wundr.