This paper examines the affordances of a component in a seri-ous game, specifically how one material design choice affectedthe interactions and opportunities for agency and learning. Thegame examined is a megagame, a large-scale (20-100 participants)social learning environment combining board-gaming with role-playing. The megagame poses participants the challenge of creatinga sustainable society, and focuses on developing participants’ un-derstanding of how different stakeholders in a regional energysystem and society are interconnected. Negotiation over conflictinggoals was a primary activity in the game, and agreements wereformalized through paper contracts. Contracts were designed toact as boundary objects between player teams, and defined theirfinancial exchanges. This exploratory study finds evidence in theinteractions between participants that the paper contract systemfacilitated opportunities for participants to develop understandingabout the interdependencies between teams and resources, andto exert agency over their role in these relations. Players activelymaintained and prioritized the correspondence between copies ofcontracts as a means of regulating both the game’s economic sys-tem in the game and their mutual intersubjectivity. Overall, thestudy highlights the importance enabling participants to experiencehow joint actions cumulatively produce future consequences, andhow opportunities for agency and negotiation educate about theongoing global polycrises of energy, climate and social tension.