Pretty fun game, I suppose this is just designed to be more of a proof of concept to get some experience for larger projects later (like how april fowl was) and in that vein I think it's really good, it's very well done technically and would be a good start if you wanted to keep working on it or do something else similar.
I did find a bug, if you build something, and then cancel the building, then the game won't let you build something in the same spot (although saving and reloading fixes this.)
The only other small request I have is a way to increase the UI size, as someone with a somewhat high resolution monitor the UI is really small and there isn't much you can do about it, especially since you're using it so often. I think adding some hotkeys might help as well if you were able to.
I also have some more complex (and critical) thoughts on the game and it's general game design and controls that I may or may not write out and put here later.