I found the mining mechanic very enjoyable to use. Got into a zen state when mining out veins of minerals at points. Well done for implementing Procedural generation in the timeframe too.
Art style is nice and fitting for the genre, lighting effects are a nice touch, and music choice is good. Gameplay concept is of course on theme.
For improvements, progression felt a bit slow. Perhaps instead of generating a new level each run, keep the old one so the player can use previously dug tunnels to get deeper faster. I'd also suggest working a bit on the UI design.
Overall, a Fun little mining game that I spent a decent amount of time playing. Nice job!