In this volume, an interdisciplinary team of researchers shares insights from three years of intensive design research resulting in a game, Beats Empire, for formative assessment of computer science and data science skills. This book follows the team through the initial design process, the development of the game, its implementation in a middle school classroom, the research that came from game data, and reflections on lessons learned and future directions. By explaining in detail the team's game design process this book offers important insights into the design of assessment games.