I can think of one made of squares; just glue eight cubes together in a ring. I am guessing that violates a constraint that Jim didn't state. On Thu, Oct 22, 2020 at 4:26 PM James Propp <jamespropp@gmail.com> wrote:

George Hart’s Celebration of Mind talk (just concluded) makes me wonder: is there a non-self-intersecting torus surface made of parallelograms?

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