The concept is really cool and a great use of the theme. I think that this game has a ton of potential to his that perfect combination of being simple enough to play around in and start learning, but complex enough to form interesting strategies and ways of playing, especially if you're looking to expand on it.
Unfortunately, I have to mimic what I see a few others saying; UI could use work, especially knowing how much buildings cost and in deploying your armies. In-game explanations of what buildings do would be nice as well, but you did put that info on the game page, which I think is totally fine for the sake of a jam with limited time.
Ultimately, I feel like this plays like the beginning of something that would massively benefit from expansion. There's so many interconnected pieces of this that there are lots of directions you could go, all of which could be pretty unique and cool! Whether you're planning on expanding it or not though, good work.