This document discusses designing for real-world participation and social interaction using digital technologies. It provides examples of installations that facilitate collaboration between people in physical spaces using touch interfaces and augmented reality. Key lessons learned include testing how people feel about sharing inputs in different contexts, designing for spectators as well as participants to encourage participation, and starting design work in code rather than paper prototypes. The document advocates experimentation and learning from other design disciplines to develop technologies that enable multi-user experiences and social engagement.