Curriculum documents in Norway suggest that early childhood teachers can use games to promote children’s mathematical learning. To support student teachers’ understanding of this, it was considered valuable to have them design games so that they could learn to recognise and utilise the mathematical potential of those games. The 21 games gave insights into how student teachers recognised mathematics in the game design process, how they deliberately incorporated mathematics into the game design, and how playing the game indicated further possibilities for mathematics learning opportunities. The design process included making, playing, discussing, and evaluating the games. The games were developed in workshops by first-year student teachers. The data consisted of the games and field notes about the design process. From the Artefact-Centric Activity Theory, the focus of the data analysis was on the internalization and externalization processes that the games could facilitate. Three games were selected for further analysis based on game design features (mechanics, story, aesthetics and technology). The results indicated some differences between the mathematics the student teachers deliberately incorporated while designing games and what the actual game could facilitate.