Avoider-Enforcer game

Summary

An Avoider-Enforcer game (also called Avoider-Forcer game or Antimaker-Antibreaker game) is a kind of positional game. Like most positional games, it is described by a set of positions/points/elements ($X$) and a family of subsets ($\mathcal{F}$), which are called here the losing-sets. It is played by two players, called Avoider and Enforcer, who take turns picking elements until all elements are taken. Avoider wins if he manages to avoid taking a losing set; Enforcer wins if he manages to make Avoider take a losing set.