Rock paper scissors

Rock paper scissors is a simultaneous hand game in which rock beats scissors, scissors beats paper, and paper beats rock. Players reveal one of the three gestures at the same time.

Mixed strategy: A strategy that assigns probabilities to multiple possible actions rather than choosing one action deterministically. Randomizing among gestures prevents an opponent from exploiting a predictable choice.
Rock paper scissors tournament: An organized competition in which players or teams contest matches using rock paper scissors. Tournament play turns the game's basic rules into repeated strategic contests.
Janken: The Japanese hand game commonly played with rock, paper, and scissors gestures. Janken is the Japanese form from which the modern international game developed.
Rock paper scissors with well: A four-choice variant that adds a well, which defeats rock and scissors but loses to paper. This variant illustrates how adding a gesture can create unequal numbers of wins and losses.
Nash equilibrium: A strategy profile in which no participant can improve their outcome by changing strategy alone. Choosing each gesture with equal probability is the game's symmetric equilibrium strategy.
Rock paper scissors lizard Spock: A five-gesture variant that adds lizard and Spock to the original game's cyclic rules. The expanded version applies the same design principle with more choices and win relations.
Sansukumi-ken: A Japanese family of cyclic hand games in which each sign defeats one sign and loses to another. Rock paper scissors belongs to this broader tradition of three-way hand games.
Cyclic dominance: A relation in which each of several competitors defeats one and is defeated by another. The game's three gestures are a clear example of cyclic dominance.
Zero-sum game: A game in which one participant's gains are exactly balanced by another participant's losses. With draws worth zero, one player's win is the other's loss.
Matching pennies: A two-player game in which one player wins when coin choices match and the other wins when they differ. Like rock paper scissors, it has no pure-strategy equilibrium and rewards randomization.

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