I had played the game close to its initial release and just came back to it kind of randomly and was delighted to find it was still receiving updates. Very nice project!
I have now completed all the content (minus winning the jackpot and maxing focus levels, cause idc about that lol). I might do another playthrough rejecting the leatherworker at the start just to see how much of a difference it makes (also read in a comment you haven't had someone beat nix farfields in hard mode, so that might be an achievement to try and grab)
A couple bits of feedback from my playthrough (I restarted my save file when I came back):
-Diamonds are extremely strange in terms of progression, their rarity and pricing makes sense before farfield gets unlocked but after that they remain a strange roadblock. I forget if it was for an extra light or extra power upgrade but getting the 15 diamonds for it was such a hassle that by the time I got that particular upgrade I had enough "rarer" resources from farfields to immediately unlock the next 3 or 4 steps of progression along that upgrade line.
-Cobalt and vermillion both seem extremely abundant for how much of them you need, with copper/iron/gold/titanium I think there's a very good balance of initial scarcity, following abundance, and scarcity again once you start running low on quartz and realize they can still have some use through selling. Cobalt and vermillion suffer pretty greatly from not being sellable. Getting your first few pieces is very difficult and rewarding without farfield upgrades in general but once you get a single farfield tool you can quickly get much more than you need and it's sad to consistently ignore these initially precious metals while titanium still has some decent value.
-It would be nice if more tools had niches to fill. It's interesting that the diamond pick still has some use in the very end game, and it would be nice if other older tools still had some incentive to be present later on. Maybe even just some awkward quests for special resources needed for endgame progression or just achievements for using inappropriate tools would be nice.
-I wish power progression was a bit more spread out, currently the spike from 5(6?) to 10 just feels too extreme and while you don't actually get it all at once you spend such a comparatively long time stuck at the max level pre-farfields so once you slightly get going there you get whiplash rocketing forward. Even though the final upgrade wasn't trivial to get it also wasn't that painfully necessary to survive as the previous ones.
Overall I love this game and really appreciate the work you've put into it. My wall of feedback comes purely from a place of love <3