I'd say this is a fantastic game. Very balanced and gives room for tactical micramanagement.
Few things You should change in the interface which suck donkey balls:
1)Making upgrading easier to do. I lost battles while trying to upgrade units. It's slow and cumbersome.
2) The controls are non responsive at times.
3)Maybe make a pause screen where you can upgrade/buy units so enemies can't overwhelm you.
Apart from that, the game is stunningly good.
Minor bug, level 3, got stuck inbetween waves because of an enemy getting stuck on the edge of the screen and I couldn't progress without refreshing
Very fun game!
Thaddeus: Who stole the gold from my pouch?