The main problem with educational games is the insufficient of playability. According to the contemporary game design theory, we analyze the online game "QQ Farm" and the information literacy educational game "Defense of Hidgeon" from five aspects: target, role, challenge, resources and tools, and interaction, trying to find out the differences between them in terms of following the game design theory. We find out that there is a serious lack of game elements in the game "Defense of Hidgeon". Six basic principles for educational game design are sum...