Something rolls toward you. Tap, and your little runner hops over it. Clear it and that's a point; clip it and a life goes, three in the bank. The obstacles start polite: one at a time, plenty of room. Then they gang up in pairs and triples, and your taps turn into a panic that somehow works. There's a rhythm to the good runs, a weird trust between your eyes and your thumb. Break it once and it's over. The screen goes still, and the only thing moving is your finger, still tapping at a world that already ended.
Something rolls toward you. Tap, and your little runner hops over it.