Really creative take on the theme and I think you incorporated it into tower defense perfectly. I would've liked to have more guidance / instruction on when / why to use larger towers. I wasted a lot of money on smaller and larger towers because I placed them in bad places because I didn't know what they would do. I also think having a pause between waves would be nice to give the player a break to re-strategize. I really like this concept though and I'd love to see it turned into a full game. Nice work!