I bought a torus shape cushion for my own certain reason. It has one hole, that hole is just different point from normal cushion, but this hole has a lot of functions. One of those functions made me happy, it helped me a lot.

A shape of torus is topologically different from a shape of sphere. One hole is also distinct mathematically. In topology, a cube and a sphere are the same things. If a sphere gets one hole, it become totally different things from a cube. In my case, torus shape made difference.