Really well done!
As it says prototype, I will offer some ideas (feel free to ignore if you don't like them):
- Some eerie music sound enhance the atmosphere a bit
- I think a bit more lore could be interesting too, maybe coming across notes scrawled on the walls by miners to fill in some back story
- I think it might be good to let players know how far the end is ... that could serve as a motivation to keep going
- Some kind of meta-upgrades to make the next attempt easier, like Vampire Survivors (very addictive)
- Finding the loot of your previous attempt (this could work even with the proc-gen, but just putting it at the right number of meters)
There is an old game called Fiend which really intrigued me for a while. Unfortunately the action sequences were very hard to control. This game has a similar style, but is much more manageable. But maybe (if you can find it) that game could give you some neat ideas to incorporate.