Rock Paper Scissors
Play against the computer, with a running score.
Play
Pick rock, paper or scissors; the computer reveals simultaneously and the score keeps a running tally of wins, losses and draws. The computer draws uniformly from the cryptographic random source โ it cannot read your pattern, and it has no pattern to read.
The game theory in thirty seconds
Against a truly random opponent every strategy wins exactly a third of decided games, so this page is unbeatable and unloseable in the long run. Humans are different: real players open with rock more than a third of the time (novices especially), tend to repeat a winning throw, and switch after losing twice โ patterns documented well enough that competitive RPS players (yes, there are championships) build exploits on them.
The practical corollary: to win against a human, throw paper first; to be unexploitable, be random โ which is genuinely hard for people, as the guide to randomness explores. Settling a real dispute? Best-of-three here, or skip the theatre with the coin flip; choosing among more than two options is drawing lots.
Frequently asked questions
Can I beat the computer at rock paper scissors?
Not in the long run โ it plays uniformly at random, which is the game's unexploitable strategy. Expect to win, lose and draw about a third each.
What is the best first move against a human?
Paper. Studies of real play show rock is thrown first more than a third of the time, especially by novices.
Does the computer react to my choices?
No. Each throw is drawn fresh from the cryptographic random source, with no memory of your history.
What beats what?
Rock crushes scissors, scissors cut paper, paper covers rock โ a perfect three-way cycle with no strongest move.