Education for Sustainable Development (ESD) has become an essential issue for schools facing major challenges such as bridging the knowledge-action-gap. Interactive simulations could help to focus on action-oriented learning. As part of a design-based research (DBR) process, we investigated the learning potential of game elements within a digital educational game for ESD we are currently developing. The final game aims to convey specific aspects of ESD ranging from sustainable land use to personal power consumption. Seven groups of 2-3 secondary school students (9th and 10th grade, n = 18) played the educational game in an early prototype phase. Following the DBR approach, students were shown screenshots of specific game situations in subsequent group interviews to reveal their conceptions and conceptual developments regarding sustainability. To analyze the causes of possible learning processes, we used the retrospective query on the learning process and qualitative content analysis. The results indicate that the observed learning processes can be primarily traced back to feedback mechanisms and the visualization of processes that would be too complex and long-termed to be experienced by students in real-life. This is how a simulation game, which makes complex interrelations tangible, can contribute to ESD. The possibility to make decisions and act (digitally) within the game allowed students to experience immediate feedback and self-efficacy. Therefore, the easily accessible visualizations and the immediate feedback are essential elements for the final game. It appears however necessary to embed the game in well-structured reflective processes. The study also contributes to adaptive game-based learning as a growing branch of research in which game elements are adopted and adapted for learning based on learner characteristics and the thematic context.