Youtopia is a hybrid tangible and multi-touch land use planning activity for elementary school aged children. It was implemented on a Microsoft Pixelsense digital tabletop. The main method of interaction is through physical stamp objects that children use to "stamp" different land use types onto an interactive map. Youtopia was developed to investigate issues surrounding how to design and evaluate children's collaborative learning applications using digital tabletops. In particular we are looking at how the interface design supports in depth discussion and negotiation between pairs of children around issues in sustainable development. Our primary concern is to investigate questions about codependent access points, which may enable positive interdependence among children. Codependent access points are characteristics that enable two or more children to participate and interact together. In Youtopia these implemented through sequences of stamps that are required for successful interaction, which can be assigned to children (codependent mode) or remain unassigned (independent mode).