There's a solid core here, and I had a lot of fun with this game! However, I do think there's a lot of room for improvement too:
- None of the levels feel very distinct, aside from the resource distribution. It would be cool to see more environmental features that the player can interact with to make mining more interesting in each of the levels.
- The mining area upgrade feels WAY too powerful and the sound when using it at the higher levels is absolutely horrendous.
- Consider adding a magnet upgrade so that less of the late game is spent retracing steps to collect gems.
To be clear, I still really enjoyed this game and I think you did a great job with it!