The current socio-ecological challenges and phenomena that are major topics of geography education, like climate change and migration, are highly complex. Maturity in these contexts requires a networked way of thinking, and a systemic competence that is difficult to develop in geography classes alone. Digital games that simulate complex systems which include the pressing issues of today's challenges may be a useful supplement to foster systems thinking. In this study, we develop a framework to assess the complexity of in-game systems. A subsequent analysis of a selection of current commercial strategy and simulation games shows how system complexity is designed differently in the various games. Based on these results, we make recommendations for the selection and use of different games in formal and informal learning contexts.