It's a truly lovely game, but I don't think cows are spawning as fast as they're supposed to. I get a new cow maybe 40% of the time, when I return to the surface, and I've run out of leather completely as a result.
I'm also getting a bit tired of combing the magma zone for quartz. I think I'd find this "quest" a lot less annoying if there was some sort of cumulative bonus for the number of times you've reached water (maybe the number of times a specific turtle has sipped the water, like a level-up system; the bonus could even be different for each turtle) -- it wouldn't feel like I was doing EXACTLY the same thing, over and over, then. I'd also have a reason to change my turtle loadout again -- now that I only have one goal when digging (find quartz in the magma zone), it doesn't make sense to mess around with turtles or artifacts anymore.
I was also hoping for the relics to . . . idk, do more? Unlock new recipes? Allow you to equip specific relics for themed effects? Allow you to build a museum that would then accumulate "donations" of quartz, with the quartz yield dropping A LOT when you took a relic out (to equip it), so you'd have to balance the usefulness of the effect with the slashed income?
Idk. I'm not a game designer. I just feel like I've run out of things to DO before finishing what I want to get DONE, if that makes sense. And that's a shame, because I've had a lot of fun with this game so far.
TL;DR: discovering stuff and messing around is really fun, and I wish I could keep doing it while chasing the last two turtles. I'm sure I'll keep enjoying the game in some capacity no matter what (it's charming and relaxing), but it could be even better, I think.