Really chill, nice visuals and music, a cool game to feel the vibe and dig away. It has clear objectives and it's very satisfying to gather the resources. This game jam is really making me consider trying making something in pico8 :)
I also think not digging up is super ok, it adds strategy in this scenario. One thing to consider is that I never felt I was in any danger. While this may be intended, and it contributed to the chill aspect of the game, it kinda made me feel that the o2 tank upgrades were just to stay a little longer down there and not for safety.
Overall great experience, good job!