Tap the bigger circle
Streak: 0
Two circles appear side by side — tap the bigger one. Get it right and a new pair appears immediately; get it wrong and the round ends there.
It sounds trivial, and mostly is, until the sizes get close enough that you have to actually look rather than glance. It's endless and quick by design — a good one to play in short bursts rather than settle into for a long session. Your best streak is saved, so there's always a number to try to beat.