I don't really get why my towers die when they shoot... and why there is no upgrade to extend their staying power. This makes the game kinda frustrating.
I also don't get
a) what mana potions are good for
b) why stunning towers don't do damage (i mean, you have to kill the knights. And the towers destroy themselves after shooting. Alas, stunning towers are a huge waste of money)
c) why placing a tower below a knight is the most effective weapon in the game
you should add an encyclopedia or something, where one can look up what everything is good for.
So, I like the idea of the game, I really do. But these few points make playing it rather frustrating.