Great game!
I like the mechanics, like you can't upgrade while defending and vice versa. It has a lot of potential. Like you can add an end goal like some kind of boss, different buildings with different stats(maybe multiple buildings in one map), more obstacles like walls and damaging areas, more variety in enemies with abilities like shooting or creating their own buildings.
I'm saying that because the game has solid gameplay without it and I'd like to see it grow into something I'd buy.
not without bugs, if you upgrade after max upgrade the game will crash, but you can fix that easily.
It's a shame that the game was submitted after the jam so it will get less ratings(or maybe I'm wrong)