In 2013 Hedmark University College conducted a research project where students from a game development project/study program developed and tested a Pervasive Game for learning as part of a class in System Thinking. The overall game goal was to teach Sustainability through System Thinking, and to give the students a real world experience with their game. It was tested on 5th and 7th graders in elementary school, spending one school day in each of the classes. This article focuses on the design of the project: how the game was developed, how the children played it and how research was designed and data collected.