Gorgeous art, cute girls :D
I think graphically, the game could really benefit from some particle effects.
Design wise, I would've liked the spawn and end points to be highlighted so it's clearer where they are. Same with when there's a new level. It's easy to miss where the new spawn points are.
I like that you can freely move towers around during the wave phase, it's a refreshing take on the tower defense genre where you just set and watch every round