We describe two games in which online participants collaborated with mobile participants on the city streets. In the first, the players were online and professional performers were on the streets. The second reversed this relationship. Analysis of these experiences yields new insights into the nature of context. We show how context is more socially than technically constructed. We show how players exploited (and resolved conflicts between) multiple indications of context including GPS, GPS error, audio talk, ambient audio, timing, local knowledge and trust. We recommend not overly relying on GPS, extensively using audio, and extending interfaces to represent GPS error. Keywords Context, mobile applications, GPS, audio, games MOBILE MIXED-REALITY GAMES We explore the design of experiences in which mobile participants collaborate with those who are online. Potential examples include remote maintenance, command and control, museum visiting and games. They key to such applications is esta...