A steel ball on a wooden board with holes in it. Get it to the ring at the far end. Fall in a hole and the board resets — the clock does not.
Five boards, one running clock.
Desktop: move the mouse over the board to tilt it, or hold the arrow / WASD keys. Phone: tilt the phone. R resets the board, double-tap re-zeroes the tilt, [ ] change the tilt setting mid-run.