Non-Rectangular Tracks

In the next Bloons Tower Defense game, not all tracks will be rectangular. The tracks will be able to be in any shape, including circles, triangles, squares, and anything else (it doesn't have to be an actual "shape" like the other ones mentioned). So that the game area can still be rectangular (since the menus might get awkward, otherwise), Nothingness will be used to surround the actual track.