Mathematical games are widely used in primary school classrooms, yet the activities that are labelled as "games" vary considerably in their structure, cognitive demands, and potential to support student reasoning. This conceptual paper offers a typology that distinguishes between pseudo-games, superficial games, gamification, and instructionally rich games. Drawing on examples from classroom practice and research literature, we argue that the presence of choice alone does not define a pedagogically effective game. Instead, instructional value depends on the nature of the choices available and their alignment with key mathematical ideas. We propose three design principles that characterise instructionally rich games, with particular emphasis on the role of strategic reasoning, embedded representations, and opportunities for students to make meaningful mathematical connections. This framework is intended to support teachers, researchers, and designers in critically evaluating and developing mathematical games that move beyond surface-level engagement to promote deep, conceptually grounded learning.