Chopsticks

You and the computer each start with one finger up on each hand. On your turn, attack or split.

To attack, drag one of your hands onto one of the computer's, or tap yours and then theirs. Their hand gains as many fingers as yours shows. A hand that reaches exactly 5 is out. Past 5 it wraps around, so 4 + 3 leaves 2.

To split, use the buttons under your hands to move fingers between them, for example 1 · 3 into 2 · 2. This can bring a dead hand back. If your total is 5 or more, you may drop five fingers, so 4 · 4 can become 0 · 3. Just swapping your hands doesn't count as a move.

You lose when both your hands are out. If the same position comes up a third time, the game is a draw. With perfect play from the start, nobody can force a win.