I got stuck while reading this:
Consider the torus sitting in $\mathbb{R}^3$ like a donut on a table.
Then you see that it is invariant by a rotation of $180^\circ$ around an horizontal axis.
The quotient by such involution is a sphere.
My question is why the orbit space is sphere?
I couldn't understand how to visualize it?
For reference I want to add this math stack question Is it possible to obtain a sphere from a quotient of a torus? - see the first answer
Thank you.