Educational games are effective in teaching, but often focus on technical aspects rather than game design. A new methodology combines Agile-Extreme Programming with game design, using expert testing to validate game prototypes. The study measured game concept, subject matter correctness, and various aspects of game design. Subject matter experts rated the game highly for correctness and question appropriateness. Media experts rated the game positively for software engineering, visual communication, and media design. Overall, the game received a good score on the Computer System Usability Questionnaire. Feedback from experts on the prototype was also positive.