Thanks for the comment! This error was one I was aware of, but I didn't think there was enough time to debug and fix it. It has something to do with the collision, and how it checks if there is a tile in the way. If you wander outside of the generated game area (not very large due to generation times), it looks for a tile that doesn't exist hence giving the IndexError: list index out of range error. Will definitely be fixing this if I continue work on this game!