At the science - policy interface there are several reasons to combine models with the participatory process to facilitate the complex policy making process but the communication of the two sides is often too hard to generate any meaningful results. In this paper we argue that to close the communication gap the rationale of the Meta – rule of complex policy making needs to be comprehended and coped with. Gaming as a participatory method can be used to organize the combined process. Through the literature review we summarize the principles of gaming and use them to analyze an empirical case where stakeholders participated in a water policy making process. A computer model called the Planning Kit Blokkendoos (PKB, in English: Box of Blocks) was used here to support the participatory process and is claimed to have had a marked impact on the complex policy making process. We conclude that the PKB tool provided the stakeholders with significant ‘room to play’ with the various policy alternatives and interweaved with the policy process.