Good game, My only critique is that it upgrades very quickly, which is great for the casual gamer, but doesn't provide a great challenge! I think Super Hard Mode needs badges too!
Great game but often the effort put in feels unrewarded, whether it's more money or more xp there needs to be some sort of short term reward so that you don't just visit the shop once every 750 kills
I am impressed with the game but it's very simple- some form of upgrading using the gold would be good. On a few levels I managed it in less than the gold medal standard, but with no reward- perhaps a system that works overall (e.g. all castles in less than 35 shots for example) could work?