Ehrenfeucht-Fraïssé games (in short EF games) represent an important tool in twentieth-century logic.
From simple to very complex, these games are delightful to play among friends and
equaly delightful for logicians, as they adapt fruitfully to a wide range of logics and structures.
We will start by describing how EF games are played in the familiar context of directed and undirected graphs.
Lesson #3 discusses examples of EF games and winning strategies for the Spoiler and the Duplicator.
Lesson #5 reformulates those strategies in terms of first order logic. Finally we present applications of EF games
in proving inexpressibility results.