More than your adherence to the theme, I'm impressed by your idea to turn to the tower defense genre and knock it out of the park!
Thanks! The original idea was a more tradicional TD where you dragged your towers around and placing a lot of towers around would slow you down. As the development progressed, we changed it to be more "puzzle-like" as it is.
Sounds like you'd easily be punished for spamming towers. I'm glad you went with a different kind of limit, which seems more forgiving!