Based on 10 years of participatory modeling experience, the authors developed a multilevel participatory modeling process that links national policy makers, local councils, and grassroots stakeholders using a combination of games and computerized simulations. The challenge was to allow the target groups to design and evaluate collective adaptations to climate change that combine new collective rules for local, regional, and national regulations. This article details and highlights the novelty of the methodological process, which allows stakeholders to codesign frameworks for their own behaviors and rules. The experiment uses games and models with soft rules and the stakeholders themselves incorporate their own perceptions both in the board and computerized games. This was shown to be an efficient way to reach assessments and proposals that are shared between local stakeholders and policy makers, and should thus help improve the design of policies to face up to climate changes.