Cool game. I like the idea that different blocks you get do different things. The presentations is really slick, as I'd expect from you.
Overall, I found the pogo-ing down a hell of a lot more fun than the jetting up. While jetting up, it just mostly felt frustrating to control. The camera whipped around too much, and the steering was really slow. The idea of getting back to the surface for air seems nearly insurmountable, because it is such a nightmare to navigate all that way with the jetpack. Especially when you keep blasting into stalactites. Having to prioritize getting blue gems for more air is way more appealing, in my opinion.
I don't mean to armchair this too much, but the game strongly encourages you to go down. It's even in the name. And then it harshly punishes you for it. The first time I played, I hit the lava and was very confused. I'd honestly consider ditching the jetpack entirely, along with the need to go up at all. It feels so much more natural if the "difficulty" increased as you got deeper and deeper. Like, fewer air gems, more hazardous blocks that take your health, but bigger rewards too. Then the skill being tested is your ability to control the pogo stick. Instead of a jetpack thing, you could hold space to do "super jumps" or something like that.
Anyway, nice work overall. I had fun with the pogo stick and mining combination, it's great. It's just the jetpack stuff I honestly find frustrating.