I played this for quite a while, and I think there's a really great game here with just a couple of bits holding it back.
The first thing I want to note is that I think there's a small bug with the mining controls. As I understand it I can click or use S, however I noticed that if I hold S and spam click the drill, it goes about twice as fast. I'm not sure if this is a bug, or intended to reward those giving themselves carpal tunnel.
I love upgrade games, so I really enjoyed this aspect of the game. The upgrades are varied and interesting, much much better than just 'number goes up' type things. Because the shop opens immediately as the inventory gets full, I did often accidentality buy upgrades as I was clicking at the same time it popped up. I think I would also love a UI icon to show how much ore I have stockpiled, not just the haul from the current run. I didn't realise there was a stockpile for longer than I'm prepared to admit haha.
The art and sound is nice, nothing stood out to me there and everything integrates nicely which is great, so I have very little to say here.
I didn't actually suss out the prospectors until I saw the GIF in the description, so a little more tutorialisation might be nice, however the penny did drop eventually.
Overall I really quite enjoyed it once I started to understand all the mechanics. There is just a little learning gap at the start where it's not completely obvious how to progress, and some small UI blockers. Aside from these small points, I did have fun. Thank you!