A PSPACE-complete Graph Nim
  We build off the game, NimG to create a version named Neighboring Nim. By reducing from Geography, we show that this game is PSPACE-hard. The games created by the reduction share strong similarities with Undirected (Vertex) Geography and regular Nim, both of which are in P. We show how to construct PSPACE-complete versions with nim heaps *1 and *2. This application of graphs can be used as a form of game sum with any games, not only Nim. 
Kyle Burke, Olivia George
cs.GT cs.CC math.CO