This study examines the design and enactment of a secondary physics unit on electromagnetism. The unit used an educational videogame to support peer dialogic engagement in a Singapore secondary school by engaging learners with qualitative physics phenomena. As an example of game-based learning, the unit includes activities and resources that organize a recurring progression of playing and interacting around science that we term "play-centered cycles." We incorporate two complementary, qualitative analyses to consider how a recurring progression of playing with and talking about science-mediated peer dialogic engagement across two separate classes. Findings demonstrate that peer dialogic engagement occurred within each play-centered cycle for both classes but that the nature of such engagement varied across cycles and student teams. Additionally, comparative case analyses of focal teams' peer dialogic engagement illuminate how the design of play-centered cycles productively supported play and learning while also highlighting emerging tensions for sustaining dialogic engagement. Findings underscore the plausibility of this approach to fostering science learning by articulating two principles for designing science learning environments that can guide ongoing efforts to enlist videogames and play in the service of talking about and learning science.