Great mechanics and game loop. I saved this one to come back later, really reminded me of Age of Empires a bit, which is a good thing. I made it all the way to level 5 I think.
My biggest thing that bothered me strangely enough was the chicken SFX when I built a farm lol. Perhaps a script with a timer of some sort to determine when to make the chicken sound so it's not playing non stop all the time. But this is awesome, well done!