Thanks for the feedback!
This is still a very early prototype. I am currently working on structuring the upgrades into a tree to stagger progression across the whole mountain range.
I am considering doing away with the timed day mechanic, and making it so that you can buy upgrades while rolling the boulder. I am open to suggestions!
It might help to have Suffering become a different resource, like... "Resolve" or something, so as to put a limit on the growth rate. Just having Suffering lead to upgrades feels like it'll be difficult to scale, and an intermediary could be helpful in slowing the rate of upgrades in a meaningful way. It works fine at first, but when you can get billions of Suffering per frame, you need something to filter that into upgrades. Suffice to say, the Strength/Weight/Suffering relationship could also use some work itself.
Also, thematically, I'm not sure you could call Sisyphus happy on a point-based system. Perhaps it would work better as a -100 - +100 scale dependent on the difficult of the boulder against the progress rate and the height of the mountain. "The struggle itself towards the heights is enough to fill a man's heart," after all, and happiness is momentary and fleeting.
Another thought is that the mountain itself should just be one stage. I don't think there's much to gain by having different arbitrary heights to climb to, especially when the point is the task itself, not it's completion. Maybe don't have the climb be infinite, there should be some action of the boulder rolling down the hill and all for the metaphor to work; a denouement where whatever buffs the player has accrued can be reset and the task can start once again. There is no height that Sisyphus could climb to that itself would provide a measure of meaning, after all.
And if I can be critical... I don't think this game properly conveys the philosophy behind the Myth of Sisyphus at all. It feels like surface level trappings used to explore an idea; set dressing for something meant to be infinite by it's nature. Like, there's a lot of commentary you could make, a lot of things that could be said, but this feels too on the nose to be witty and too aesthetic to be meaningful.