Abstract. Public transport can be a place where commuters feel rushed or stressed. Missing your train, a delayed bus or crowdedness at the station does not induce happiness among most people. As a consequence, prosocial behaviour like offering someone a seat is displayed less often. We discuss the design and design process of MirrorMe, a simple communal game to induce positive mood of commuters. MirrorMe aims to increase prosocial behaviour through mimicry. Commuters are challenged to “make a face” and thereby connect to other commuters. MirrorMe will be installed in a public display close to a train station enabling access to all commuters and passers-by. This work addresses the need for games and play in public setting to stimulate prosocial behaviour. It exemplifies how multidisciplinary HCI approaches in a gamejam setting can contribute to real life challenges. We conclude with open questions for impact evaluation in future work. Full conference paper available here.