Cool game.

Just a few ideas you could add if you want.
A pause button.
And a mute music button.
And perhaps add an upgrade that gives you some way to get back to the shop and back to your last place in the mine faster. Because once oxygen isn't an issue then it's just annoying having to run back to the start again.

It looks like you may plan to add more.
If you do, I look forward to more. 😊