Rock Paper Scissors
Play best-of-three rock paper scissors against the computer
About this tool
Play rock paper scissors against the computer in best-of-three, five, or seven series. The computer's choice is completely random on every round — it uses no strategy, no pattern recognition, and has no memory of your previous choices. This makes every match statistically fair, with each player having an equal expected win rate over the long run.
Rock Paper Scissors (also called Roshambo) is a hand game played worldwide to make quick, fair decisions. The rules: rock crushes scissors, scissors cuts paper, paper covers rock. Each choice beats one and loses to one, creating a balanced three-way cycle. The game is a zero-sum game with no dominant strategy — in a purely random game, each player wins one third of non-draw rounds.
Human players are actually quite predictable — research shows people throw rock most often (as the default "strong" choice), especially after a loss. After winning, players tend to repeat their winning move. After losing, they tend to switch in a predictable pattern. This is why real Rock Paper Scissors tournaments involve genuine strategy and psychology — the World RPS Society holds annual championships where these tendencies are studied and exploited.
In competitive play and research on game theory, RPS is used to illustrate Nash equilibria: the optimal strategy in a zero-sum three-choice game is to randomize uniformly (choose each option with 1/3 probability). Any deviation from this can be exploited by an opponent using a best-response strategy. The computer in this game plays exactly the Nash optimal strategy: purely random.