Rock Paper Scissors

Rock paper scissors is the classic hand game for settling who goes first: rock blunts scissors, scissors cut paper and paper wraps rock. Here you play against the computer, which picks its move with a fair random draw — no peeking at yours. Play one round or a best-of-three or best-of-five match, and try the five-move version with lizard and Spock, which makes draws less likely.

How to use this tool

1. Choose the classic game or the lizard–Spock version.
2. Pick your move, or let it be random each round.
3. Choose one round or a best-of match, then press the button.
4. Read the result and the rule that decided each round.

Formula

P(win) = P(lose) = 1/3 and P(draw) = 1/3 in the classic game; 2/5, 2/5 and 1/5 with lizard and Spock

Against a uniformly random opponent every move is equally good: each beats one move and loses to one (two and two in the five-move game). The computer's move comes from an unbiased secure random integer; draws are replayed in best-of matches.

Example

You play rock and the computer plays scissors: rock crushes scissors, so you win. In the lizard–Spock version, lizard poisons Spock but Spock vaporizes rock, so each move has two moves it beats and two it loses to.