idk what's wrong with me, I can't stop playing Sisyphus games. Actually, I like this one the best so far because rolling the boulder is a matter of skill, and it feels like your fault when it starts rolling back down, but the physics system makes it chaotic so the boulder can go over your head, at which point you're scrambling back to retrieve the rock in a Getting Over It kind of way. Also, another subtle design bit that I like is that the boulder's surface isn't uniformly round, which makes it a constantly dynamic challenge as you're rolling it uphill.
EDIT: Yee