The idea is great!I loved it. I'd only fix a few things.
The shop is confusing at first, I don't know how many resources I have (I only know if I can buy things or not) and the controls are confusing, the game tells you you play with Z and X, so I was trying to buy with Z, X, Enter, mouse click, even Up and Down arrow and nothing worked until I started randomly hitting keys on my keyboard and I figured out it was the Space Bar. It's not even mentioned in the description of the game so you might want to add it.
Drilling doesn't feel satisfying and it's the main part of the game. it can easily be fixed by making some particles if you drill a rock and also making the block degrade or even shake as you break it. I know it sounds simple but it would add a lot to the player experience. Otherwise the player doesn't even understand if the drill is working or if that block is not destructible at all.
Exploration: You made a cool world, cool mechanics, I get that the theme of the jam is to go deep, but after the jam ends maybe consider removing the "force to go down" and leave it as an exploration and mining game, it looks so cool and it has the potential to be an exploration game and I'd love to play it. Of course it's your decision but maybe add an "exploration mode" that allows you to play without the constant camera pushing you to the bottom, just mining, attacking, upgrading and exploring.
Also, one shot kill enemies feel really cheap. It's a bit frustrating to just die to a bug after almost reaching the bottom and having to start over again. Maybe add more enemies but also 3 hearts (chances to get hit before dying).
Other than that I think you have a cool base for a mining and exploration action game, I really enjoyed it, if you add more content (like more treasures or blocks to mine) I'd definitely play it again! good job!