Love this game! awesome style and its a clear improvement from the last time I tried it :) I also like the map addition.
The complexity grows too fast for me personally. I think there is very little time to learn more than main mechanics from the first level (maybe add at least one more wave or like a mini boss). Also the towers seems to change their focus on the closest enemy. I would recommend to stick to one target until its out of the dmg zone.
I really like the game stile and direction the game is moving. The game does look really good imo, but the balance and fairness is the area I would focus on improving.