Many designers, policy makers, teachers, and other practitioners are beginning to understand the usefulness of using digital games beyond entertainment. Games have been developed for teaching, recruiting and to collect data to improve search engines. This book examines the fundamentals of designing any game with a serious purpose and provides a way of thinking on how to design one successfully. The reader will be introduced to a design philosophy called Triadic Game Design.; a theory that all games involve three worlds: the worlds of Reality, Meaning, and Play. Each world is affiliated with aspects. A balance needs to be found within and between the three worlds. Such a balance is difficult to achieve, during the design many tensions will arise, forcing designers to make trade-offs. To deal with these tensions and to ensure that the right decisions are made to create a harmonic game, a frame of reference is needed. This is what Triadic Game Design offers.