Would be great if you could better distinguish the available upgrades (e.g. 1/2) from the finished ones. The buildings part does come a bit early while I'm still "overwhelmed" with the starter mechanics. The game is addictive and the "one more round" feeling is well implemented.
Not sure when a mine starts over and also not sure what the arrow icon means in the mine.
I build the buildings but didn't realize I had to dig tunnels to make them operational.