📚 Practice Mode

I was a 19th century German mathematician and astronomer. I developed a lot of math: there's my configuration, formed by two mutually inscribed tetrahedra, my transformation in number theory, my transformations in projective geometry, my function, and my inversion formula. Pretty nifty, eh? You're probably most familiar with the strip named after me, a two-dimensional surface with only one side. Who am I?