As Gee and others have argued (Gee 2003; Squire & Jenkins, 2004), games offer some powerful advantages as learning environments. Perhaps the strongest determinant of learning is time on task (Bloom, 1974; Carroll, 1963), the amount of time the learner spends processing the educational content. If this processing can be embedded in a game and if the game is one that learners want to play, time on task is increased without extrinsic motivators, such as rewards, punishments, or submission to authority. Despite the potential of educational games, after teaching five iterations of a learning technology design (LTD) course at the University of Colorado, we have learned that educational game projects come with unique challenges. In this chapter, we highlight the key issues and present a way to mitigate problems by focusing on what we call gamelets, designed using an approach that centers on simulations.