Sling

pull, let go. it lands where the slot was going to be.

sling each digit into the drifting slot that wants it, for thirty seconds

A slingshot takes one instruction from you and it takes it all at once: the direction and the stretch at the instant your thumb lets go. After that the chip is on a path nobody can steer -- gravity pulls it down at the same rate whatever you did, so the entire flight was already written in that last moment of contact. The slots, meanwhile, do not wait. Aiming at where one of them is guarantees the chip arrives where it was, so the pull has to carry a guess about the future in it, and the guess is locked the moment the band goes slack. That is the whole difference between this and pointing at something: a dial can be corrected while you are still holding it, and a released band cannot. Every attempt leaves its line of flight behind, so a run ends as a record of predictions that can no longer be changed.

Concepts: gravity, trajectory, momentum.

An interactive you play with one thumb, on Wundr.