The Big Picture

One idea ties the whole lesson together: when your best move depends on what others do, you are playing a game in the mathematical sense. A firm setting prices, a country sizing its defense budget, a driver picking a lane — all of them. And almost every such game settles into an equilibrium, a point where no one can improve by moving alone.

Today this math runs auction design, antitrust rulings, and matching systems for school places and organ donations. Rock-Paper-Scissors is a tidy example of a zero-sum game: one player's win is exactly the other's loss, with nothing created or destroyed. Scale that thinking up and you get modern economics, which is largely applied game theory.