No major bugs, but definitely unpolished. With more attention to detail this could have been a great game, but the lack of even basic features like unit health is frustrating and damaging to the play experience. Additionally the balancing of units (both enemy and player) as well as the length of cooldown timers seems to be slightly off. As it stands the "engine" seems fine, but the fun-factor, game balancing, and detailing steps seems to have been skipped. This seems more like a "proof of concept" than an actual game.
I don't normally like this type of game, but this was actually pretty fun. Levels 40+ were challenging all the way to the end even with max upgrades and weapons. Nice job.