This paper proposes a Mobile Augmented Reality application to engage students in STEM education. With a design research methodology, the SolarSystemGO game, initially designed to promote learning about our Solar System, is being developed by undergraduate higher education students supervised by higher education teachers from a Portuguese polytechnic. After several cycles of implementation of the game (design research cycles), which took place over two academic years, we argue that the SolarSystemGO game can be a resource to develop mathematical contents in formal and informal learning environments. Based on our research and experience in the field, we sustain the importance of developing Mobile Augmented Reality games that engage students and motivate them to learn interdisciplinary subject matters adequate to primary school syllabus.