Microcosm explores the potential of responsive, evolving games through the lenses of play theory and cybernetics. It aims to provide an engaging play experience while supporting the exploration of dynamic networks. It is inspired by biological models of cell signalling and neural networks. Building on the framework of play theorist James Carse, microcosm is an attempt to create an infinite game that is played not to be won, but to keep all participants in play by continually shifting the relationships and boundaries that constitute the game. Microcosm is populated by virtual organisms that play with the boundaries between organic and artificial, component and whole, human and non-human.