It could use a menu button while in the game. On hard, once you get to about level 45 it gets easier, not harder. Soo much money you can upgrade several Boss turrets to 100K damage, and nothing can get by. Good game, but I don't know if I'd want to play again if badges were applied.
 "Flying Gold Collector!"){kind=icon}
 "Whiteboard Tower Defense"){kind=icon}