Nice, clean fun, but PLEASE put that "back" button somewhere else, or rename it, because I've accidentally went to the menu and interrupted my highest wave runs about ten times already, just trying to close the Shop.
I think it would be helpful, if you guys made a button for upgrading 1000 hero levels. I'm only at Phthalo yet, but I could already welcome that feature, because it gets kind of frustrating when you level up all your heroes' levels from 200 to 2000 using ctrl.
 "Infinite Arena"){kind=icon}
 "Clicker Heroes"){kind=icon}