This is quite impressive for a solo dev project! That said, the game isnāt really in a playable state at the moment, even as a prototype. It mightāve helped to get a few people you know to playtest it.
It seems the trees are bugged... for me, the oxygen zone appeared in the middle of the trees instead of around each one.
The money balancing is pretty harsh. You dig slowly just to find items that arenāt worth much. On my second playthrough, I invested everything into upgrading the shovel (which is very expensive), but the improvement wasnāt very noticeable.
The concept is interesting, but the gameplay became frustrating after a while because progression felt too slow. Honestly, it mightāve been better if the game was unbalanced in the other direction, giving the player too much, just to make testing the core idea more enjoyable.
Still, great job! Maybe next time, try to deliver something more playable, even if that means reducing the gameās scope. Playtesting and making sure the experience is fun are important parts of development too.
Note: for those who wonder, you press the F key to put items down.