this game is really cool! I think it would be cool if you could like add towers to defend yourself like a tower defense game or upgrades to make you faster/bigger. Overall this is really great! Good Job!
I honestly have no idea how to do that with one button, maybe you could add a popup every x points to give the player an option to spend points to get a randomly placed tower? I can't really think of a good way to choose where to place it, but it's a start. I didn't mention this before, but the main menu and all the different gamemodes are really cool.