 Finally, among the introductions to game semantics for PCF and other languages, we suggest Abramsky 1997; Abramsky &amp; McCusker 1999. The latter also contains a description of the applications of game semantics to imperative languages, notably Idealized Algol. Other excellent introductions to game semantics are Hyland 1997 and Curien 2006. A broad account of the use of games in the semantics of programming languages with many pointers to Lorenzen games, and intended for a philosophical audience, is Jürjens 2002.