  Rock-Paper-Scissors (RPS), a game of cyclic dominance, is not merely a
popular children's game but also a basic model system for studying
decision-making in non-cooperative strategic interactions. Aimed at students of
physics with no background in game theory, this paper introduces the concepts
of Nash equilibrium and evolutionarily stable strategy, and reviews some recent
theoretical and empirical efforts on the non-equilibrium properties of the
iterated RPS, including collective cycling, conditional response patterns, and
microscopic mechanisms that facilitate cooperation. We also introduce several
dynamical processes to illustrate the applications of RPS as a simplified model
of species competition in ecological systems and price cycling in economic
markets.
