This was awesome! I really liked mining around and finding ores, the upgrades were pretty good too. The spider in the crate next to the gold outside of it particularly spooked me, so that was pretty good. The sound design was also really good and helped create a sense of atmosphere.
I think I expected the jetpack to work as a tool to ascend but it just prevented me from taking fall damage, I think something to be able to use to get back up without having to mine would be a bit nice, just to clear higher gaps caused by breaking dirt.