Fun at first, then little more than fireworks
The main problem with this game is that there is absolutely no variation in the towers. Each tower does exactly the same thing, with slight variations in stats. The empty enviroment is fine, considering that your towers can be damaged and destroyed, but wall-building would have made it far better. The gameplay is very smooth and the music is good, but any TD where the enemies have more variations than the towers is doomed to failure.