1. Must involve either dimensional travelling or another dimension in general.
2. No limit to how long you spend developing the game (until submission ends).
The idea of trans-dimensional travel has entertained the thoughts of many. From the ancient Greeks with Taurtarus to the Christians belief in hell. To you what would trans-dimensional travel be like? Would there be any consequences? (Doom for example). What would other dimensions look like? These are just some ideas to help you, feel free to disregard them.