This paper describes the design of SCORPIODROME a mixed reality game for groups of 3-4 children aged 11-14. SCORPIODROME is designed for social gaming; i.e., computer gaming that is intended to support and trigger social interaction between players to occur within and around playing the game. The paper discusses some of the lessons learnt from this design process and how SCORPIODROME paves the way towards the development of a whole class of mixed reality games. Finally, we reflect upon some of the methodological issues encountered. Categories and Subject Descriptors H.5.2. [User Interfaces] Graphical user interfaces (GUI), Interaction Styles, User-centered design. H.5.1 [Multimedia Information Systems] Artificial, augmented, and virtual realities General Terms Design, Human Factors Keywords Social Gaming, Mixed Reality, Interaction Design, Children.