I like the basic conceit here - slowly descending deeper down the cave as you gain oxygen is an interesting structure. The game’s main issue, I think, is that it doesn’t play into that structure quite enough. On my first attempt, I beat the game in 11 runs, and on my second I beat it in 5 (and would’ve beaten it in 4 had I not accidentally walked into an enemy, which kills you very quickly). I never used bombs at all, and the only upgrade I ever had to buy was oxygen. I think maybe the money mechanic is responsible, since it means all I had to do each run is collect the ~8 gold you can easily get at the top of the cave to build up the 13 or so seconds of oxygen you need to finish the game. Maybe oxygen upgrades could be found in the map itself, to give more incentive to explore instead of just diving straight down? Overall, though, this is a good start, and it feels nicely polished! I just think the design doesn’t quite do its concept justice.