Snake

Steer with arrow keys, WASD or swipe — eat food, grow longer and beat your high score without crashing.

Snake predates the phone it made famous. The arcade original was Blockade in 1976, two players walling each other in, and the single-player version reached a mass audience when Nokia preloaded it on the 6110 in 1997 — one of the first games most people ever carried in a pocket.

The difficulty curve is built into the rules rather than added on top: every apple lengthens the tail, so the board fills with your own past decisions and the space you have left to manoeuvre shrinks as you succeed. Good play is mostly about not trapping yourself — hugging the walls and filling the board in a boustrophedon pattern keeps a route open long after greedy chasing has sealed you in.