The development of a serious game combines the skills of numerous disciplines, from subject matter experts on the topic being taught; to story developers, game designers, and software developers; to instructional designers, educational assessment scientists, and others. This section provides commentary on the Intelligence Advanced Research Projects Activity’s unique game development program, Sirius, where multiple games with the same training goal were independently developed and tested by different teams. We compare the experience of two of these teams not only in game design but also in how skills of various disciplines were woven together to produce and validate their games. Lessons learned are reviewed to provide guidelines and takeaway points to assist game development practitioners in their future efforts to create effective serious games.