The use of educational games for teaching and training is nowadays well-known, although its effectiveness in terms of learning and motivation has not been firmly corroborated. A first reason for this is that research on instructional design research often does not reach the fields of game development and game design. Consequently, instructional design principles that have proven to be effective are often not incorporated in educational games. A second reason for the mixed results on the effectiveness of educational games can be found in the way instruction in such games is offered. To our knowledge, educational games rarely account for individual differences between players and research on adaptive educational games is rather sparse. This paper focuses on adaptive approaches in educational games and discusses various player and gameplay characteristics that can be integrated in a framework that conceptualizes player-centered adaptivity in educational games.