This was visually very nice game. Not one for incremental games though I did take a good amount of time playing this. I liked the pixel art and good uuse of 3d drills for the moving parts very clever. I think the rock overlay though was slightly intrusive in the sense it was hard to see the bottom sometimes or see if I was missing any ore which made it difficult and kept having to mess with camera which I don't know if that was intended. I think the overlay at the top was fine but the bottom kept getting in the way.
The upgrade system felt good. The ui for it was nice and easy too. I really enjoyed the modular building. i myself made a game similar so I do like modular game designs in that asepct. If you do continue I think if you somehow make it where you could control the drill more that would be very cool.