The authors developed a game prototyping approach that allows learners to collectively conceptualize, create, and test a game prototype by completing a series of formative problem-solving tasks alongside a designated sprint process. It is positioned at the intersection of design thinking and gamification, building on their mutual focus on constructivism and problem-based learning. With the help of focus group data, this chapter investigates how game prototyping enhances critical thinking in learners. Findings suggest that game prototyping can contribute to the development of critical thinking skills such as social skills, reflection, and entrepreneurial thinking through the application of structured teamwork, milestone planning, and bricolage. The gradual development of these skills ultimately leads to confidence building, which can trigger changes in critical thinking dispositions that turn learners into confident decision-makers and problem solvers. The authors also aim to make recommendations for the adaptation of game prototyping beyond the context of this chapter.