Definitely need to change the tower AI to attack monsters with weaknesses to that specific tower. Having 5-7 fully upgraded arrow towers wailing on trolls while grunts stroll by without getting hit just ruins the entire game.
Terrible, only thing that makes this game hard is the awful controls. Having to stop/slowdown to aim or fire is just stupid. Need to make it so you move with A/D or Left/Right and it would be pretty good.