There is a growing interest in videogames for ethics education as they can provide a safe yet meaningful space for players to practice moral choice. A well-designed game can immerse a player in a world and challenge them with difficult moral choices, but poor design can negate this challenge by making in-game morality merely a strategic choice made to win, instead of for its own sake. To establish which design factors are most important in maintaining moral engagement, we will implement a variety of games based around a common set of moral narratives and test them with human subjects, recording their choices. The outcome will be a set of validated design principles for the creation of games for ethics education.