Excellent game! I am a big fan of tower defense games and this was a great take on the genre and concept! The art and music hit their marks, and I especially like how the music ramps up over time!
My only critique (and I mean this in the most constructive way possible) is to maybe restructure balancing. I tried a few different setups strategy-wise, and I found a lot of success with just clumping towers together instead of strategically placing them.
Besides that, it's a fantastic game and proof of concept!
Excellent Job and Game On!