Congrats on finishing a game in 48 hours!
The core idea is sound, playing on the exponential meaning of "power" is very clever but I feel like the design didn't fully accomodate for it. Why to use anything higher than "2 shots"? It would have been nice if we had to do some math to find the best possible combination of shots, perhaps the castle may attack the outside units as well!
Besides that, nice job on the animations and sound effects!