This is a great base for a game. It's well designed, looks nice and just works. But in my opinion it has some problems.
So I guess the world is randomly generated. This makes for a lot places where you can't even catch the oxygen pockets, making it frustrating. I also like the score mechanic where you get more score with less oxygen, that is just great design wise, but is canceled out with the fact I can't really control my player and make a decision to take that risk for more score. I want to take that risk, but I can't.
If I could control my character more, I think it would work a lot better. Then I could have more decision making in the game and thus have more fun thanks to me actually doing something in the game. I also think you could add mechanics on to the game then to give it more content. Would actually see it as a really cool roguelike game, something like Downwell.
Good job, it's a good basis for an actually good game.