Creating a Tower Defense game for a game jam is an awesome achievement by itself - they are hard to balance right in my opinion. You managed to make good and clever use of the theme on top of that! The music was fitting and keeping in the background, which is very important for any TD or puzzle game in my opinion. I liked the idea of managing my only power source/tower. Good job!
I did not get too far in the game, unfortunately. This may very well be the fault of the player, however. I felt a punishment for selling towers a bit too cruel, considering you have to constantly juggle the resources. That's my only complaint.