Great job submitting a game! I like the idea of exploring the underground then going back up through the progress I've made to buy upgrades and dig further. As someone else pointed out, I think the game ends a little quick to be able to have the main loop kick in. One thing that initially confused me was not being able to dig up. I like what you did with the visual style and with the player vision restriction, I think the vision was my favorite upgrade.
One of my upgrades always needed to be the health / pick durability to actually win since I ran out so fast which only left one upgrade feel like a choice. I can see the potential and I had fun playing! Thanks for participating!