Hi! Thanks for your kind words!
The left gauge is fuel, which is replenished by visiting villagers. The right gauge is a differential altimeter, which shows how far your neutral buoyancy point is from your current height. I might update the game description to mention that.
I've just shipped a post-jam patch that tweaks the controls a little (you can now hold down climb/descend over time), improves some of the presentation, and allows you to maintain more momentum coming out of air streams - level generation is pretty roughshod in terms of air stream placement, and prior to this change, I think many players were doing most of their movement via lateral thrusts instead of just using that for adjustments.