> But somehow when you collapse it, you still have a 2pi rotation! It's just that now it's a 2pi rotation in xy rather than in zx. No matter what you do, if you

> But somehow when you collapse it, you still have a 2pi rotation! It's just that now it's a 2pi rotation in xy rather than in zx. No matter what you do, if you collapse the rotation path to be the identity on the +z vector, the resulting path rotates _some_ vector by 2pi, instead of keeping it at the identity. Oh, this is lovely! That's the first good visualization I've seen for the issue. Or at least the one that finally clicked for me...