This game held my attention really well. The short runs make you keep wanting to upgrade and just do a little bit better next time. I also was a big fan of the music. It definitely captures that old gameboy era with simple tunes that just need to be earworms to work.
My only complaints were probably with the jittery camera when descending. It got more tolerable with pickaxe upgrades, but I probably would have kept the character bouncing upwards but made the camera only go downwards.
The scrolling back up to reveal your path down once your time runs out is a nice touch too, but once you start digging pretty deep it ends up taking a while to get back to the top.
Overall, really nice solid entry. Great work!