Players often have playfulness and motivation to play and make games on their own. By tapping into these instincts and guiding players in designing their own games to solve a problem, new models of collaboration between designers and players can be unlocked. In support of this, we present results from a five week case study with 25 children aged 8-10 where they designed their own games within a given context. This ongoing exploration resulted in three design themes: 1) This Setting a common goal helps people design together, in this case using sensing data. 2) Focusing on spontaneity through autonomy. And 3) Supporting player mobility with the artefacts. We hope this ongoing exploration can be a starting point in aiding designers to guide players as designers.