Super polished and mechanically deep! Wow, this is very impressive for one week, you guys did amazing work here! For some feedback, I kept accidentally clicking a random upgrade item when a wave finished while I was placing buildings. I think a "UI cooldown" would help here, where I can't choose an upgrade for at least 2 seconds when it shows up, haha.
The building system is cool, but it is weird that when I unlock a production building from the upgrade popup, I can't immediately build it, I have to wait until I unlock a unit that uses the related resource. Would much rather start stockpiling immediately so I'm ready for when I unlock a unit building.
Lots of replayability here, I had a good time!