Planning a city is a complex task requiring collaboration between multiple stakeholders with different, and often conflicting, goals and objectives. Researchers have studied the role of technology in group collaboration for many years. It has been noted that when the task between collaborators increases in complexity, such as in a decision-making process, the use of computer technology could either enhance, or disturb, the collaboration process. City Game evaluates the impact of computer interfaces on a multi-objective negotiation problem. Using a tangible user interface (TUI) is more effective for multi-objective group decision-making than a graphical or multitouch user interface; this project will focus on designing and developing a TUI and a serious game for an urban planning scenario. We will test the game on different computer interfaces to evaluate the decision-making process between different collaborators with conflicting objectives.