We compared students' learning gains in authentic seventh-grade classrooms (N = 144) in 4 different interventions that incorporated a computer game that aims to teach players to solve linear equations. Significantly higher learning gains were measured in the implementations that were specifically designed to mediate the attribution of algebraic meaning to objects, actions, and rules in the game by engaging students in analogical mapping between these constructs and their algebraic counterparts and an exploration of the boundaries of this isomorphism. These findings suggest that learning disciplinary content and skills from a digital game requires learners to attribute disciplinary meaning to objects, actions, and rules in the game. Moreover, this process does not necessarily occur spontaneously and benefits from instructional mediation.