fun little game! definitely think the core loop could be a touch more refined - like what mumin said, some familiarity between loops would help - but elsewise despite its simplicity i had a remarkably good time!
the little touches (like the music synchronizing with earlygame pick-swings) and the generally tight gameplay, save for a few bugs, were all nice to play around, but at a certain point i felt like the win state of the game was totally up to chance; the portal(s) could be anywhere, and you could just accidentally choose not to go the right direction!
i love breaking rocks, though, so that didn't bother me too much. good game, i like the idea!