>>289878319
I don't remember your post, but we think alike. I actually put together the demo in like 20 minutes with vrchat udon to track the avatar hip bone, a configurable joint and some particle systems. I'm actually pretty impressed with how easy udon makes it to experiment with body tracked objects. Feet saber, elbow saber, mouth saber, all equally as easy. Network sync and actual beatmaps and scoring harder, but I'm 100% sure someone is working on porting full beat saber to udon right now.

For a more wholesome idea, I was thinking of ways to make hula hoops work. Problem is I don't have a real hula hoop to know how the motion works. Also unity doesn't have a good hoop collider, so not sure how well a mesh collider would work, plus a hip collider that's not just a simple capsule.