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A Clifford Torus: a torus lying on the "surface" of a 4D hypersphere.
Inspired by Thomas Banchoff's book "Beyond the Third Dimension:
Geometry, Computer Graphics, and Higher Dimensions", Scientific
American Library, 1990.
https://en.wikipedia.org/wiki/N-sphere
https://en.wikipedia.org/wiki/Clifford_torus
https://en.wikipedia.org/wiki/Regular_polytope
Written by Carsten Steger; 2003.