It's quite easy so far, level 6 without nbuying anything or using any perks; although now I was clicking frantically at my enemies and suddenly the levle up screne apperas and before you know it I have +3 armor perk; make shoot a hold feature, not a button bash thing; that way menu's can still annoyingly appear without warning. Also, with the menu and decent painted backgrounds, you'd expect there to be more than stick figures and crappy animation.
I don't like facebook sorry, also, took til level 25 to actually fully grasp the mechanic and then realise it's faster to try when you're not sure rather then think about it more thoroughly
Fun that you make the screen change and all, but your game still sucks. It adds difficulty but it would to any game, so create a fun game with this instead of a default dodge game.