Flywheel

Flywheel hands you a single tap and, unusually, lets your own skill decide how hard the game gets. A wheel spins with a marker on its rim and a strike zone at the top; you tap each time the marker sweeps through the zone. A sloppy-but-legal tap keeps you alive, but a dead-centre, perfect one feeds the wheel momentum — it speeds up, the next beat arrives sooner, and your score climbs. In other words, the better you play, the faster and tighter it gets, so you are literally authoring your own difficulty curve, one perfect tap at a time. Miss the zone entirely three times and the run ends. The counter-intuitive discipline is to settle into the rhythm rather than chase it: watch the marker, let its motion cue your hand, and as the wheel accelerates, start tapping a hair early to meet the shrinking window. It is free, instant, and made for one thumb in the browser, and it remembers how fast and how long you managed to hold control.