I forgot to mention one thing!
I wasn't too fond of how the wheel upgrade was handled at one point.
I often just needed a stone - which wasn't a problem when the drop chance was 50%. But then I upgraded the wheel, and... the chance dropped to 30%, and then even lower.
That was a bit frustrating, because the "upgrade" actually slowed down my progress. Either I misunderstood something, or this needs addressing. For example, maybe allow players to temporarily "disable" such upgrades, or something similar.
I realize the idea is to give me higher-tier resources, but, oddly enough, they’re actually less valuable. That’s because I can craft a wider variety of items from the basic ones, whereas the complex ones limit my choices.
Sorry for the criticism. I wouldn't be writing all this if I didn't like the game :)