In this work, we explore how programmable playground artefacts can affect social dynamics and power structures in an outdoor play setting. A set of re-programmable artefacts and a graphical programming interface were designed and developed for the study. Twenty children were invited to co-design and explore the interactivity of the re-programmable devices. They tested how they could play with them, and were asked about how they would re-design and repurpose the artefacts and the scripting interface for their way of playing. Through a thematic analysis of the observations and group interviews, it could be seen that an implicit social role emerged, centered around the use of the programming device. This role took on a guiding and supporting role, rather than a leading role. By deliberately designing for this ‘gamemaster’ role, this understanding may be useful in future design of technology for public and outdoor play.