The ability of educational games to promote students' engagement in learning and practice depends on perceived enjoyment of those games. This study investigated high school students' perceptions and enjoyment of games within the Writing Pal intelligent tutoring system. In accord with research on motivation, results showed that perceived helpfulness and difficulty of the games were the main predictors of enjoyment, whereas graphics quality and writing apprehension were not. Perceived difficulty was most salient for generative practice games in which students had to apply strategies to write original text. [This paper was published in: "Proceedings of the Twenty-Sixth International Florida Artificial Intelligence Research Society Conference" (p.515-520). Association for the Advancement of Artificial Intelligence, 2013.]