CONTEXT: Serious games have gained popularity as an innovative participatory approach to explore the complexity of social-ecological systems, managing the trade-offs between economic and ecological targets. Serious games can be abstract and generic, or more complex and specific. They can be used to raise awareness, increase shared understanding of options and risks, and/or commitment to common goals. OBJECTIVE: We here aim to clarify design principles applied in the FORCES game (Farmer Options and its Risk in Complex Ecological-Social systems) as single-player game to be easily adaptable to diverse (upper) watershed contexts. Three steps involved are game design (balance generic and site-specific information), game use in (and possibly adaptation to) specified context(s) and evaluation of contextualized impacts. METHODS: The FORCES game design was based on three contrasting watershed case studies in East Java, Indonesia, rather than on single, specific case study. Game development consisted of preparation (defining the context, generic core issues and game objectives), development process (ideating, setting the actors, resources, elements, and mechanisms), and assessment (prototyping, exploration of solution space, game trial and player feedback). Fifty-five smallholders played the FORCES in three landscapes to test the game's performance and impact on participants' insights. Therefore, we recorded every game session and performed pre- and post-game interviews for each participant. RESULTS AND CONCLUSIONS: The developed FORCES game focuses on decisions of individual farmers involving plot-level plant (annual crops, trees) choices with financial cost-benefits consequences and links to ecological impacts on the litter layer, water balance, and erosion. The FORCES game was successfully applied in three distinct landscapes, demonstrating its adaptability. The game's generic water balance supported the transferability to different contexts, while fine-tuning of plot management options to reflect local variation was simple due to the solid underlying game mechanics. According to players, the game reflects local dynamics in the landscapes and provides a realistic experience, triggering participants to make decisions close to their real-life choices and learn from the consequences. While the game has limited representation of social interactions due to its single-player design, FORCES allowed relational values to be recognized in players' responses. SIGNIFICANCE: Balancing the combination of generic setting with easily adaptable site-specific elements in the game design plays an essential role to increase game adaptability and reusability to different locations. FORCES adds to the growing array of games that can be used to support farmers' participation in higher-level decision-making processes to secure environmental services in productive landscapes.