As part of this design research project, ׳Commonopoly ׳ was developed to translate the complexities of collective landholding and multi-stakeholder urban development into a more tangible, interactive format. Rather than functioning purely as a game, Commonopoly operates as tool—one that makes visible the dynamics of negotiation, trade-offs, and shared decision-making at the scale of the urban block, and tests out different and unexpected possibilities. Set within a low-density neighborhood on the verge of transformation, the game casts players in the roles of the Homeowners’ Co-op Representative, the Developer, and the City Planner. Each player has distinct motivations—preserving community stability, generating profit, or delivering public infrastructure—but they must navigate a shared space where their actions are interdependent. Players make strategic decisions: pooling land into a trust, rezoning for higher density, acquiring properties, or allocating public resources. The game board—a single urban block—serves as a testbed where different development strategies can unfold over time, including Add & Repair, Shared ADU, and Demolition & New Build approaches. Commonopoly is not intended to predict outcomes, but to simulate the shifting relationships between stakeholders, land parcels, and incentives. It opens up a space for dialogue between actors who might otherwise approach redevelopment from isolated or oppositional positions. For residents and co-op organizers, it offers a way to visualize and debate future scenarios without the abstraction of planning jargon. For developers, it illustrates how profit can be aligned with public benefit when working within a cooperative framework. For municipalities, it models how regulatory tools—zoning, tax incentives, and public investment—can be used strategically to support inclusive growth. The game can been used in workshops and public forums as a way to surface concerns, explore possible failures, alternatives, and build mutual understanding. In this context, it serves both as a communication device and as a means of prototyping policy. By embodying different roles and constraints, players are invited to test unfamiliar positions, confront unintended consequences, and imagine new alignments of interest. Ultimately, Commonopoly extends the central ambition of the project: to reframe the urban block not as a static object of planning, but as a platform for cooperative agency. Through play, stakeholders can explore what it means to share land, redistribute value, and shape urban change from the ground up.