dihedral (2,2,n) · 48 cells
(p,q,r) with
1/p+1/q+1/r > 1. (2,2,n) is the infinite family; tetra/octa/icosa
are the only three exceptions. Schwarz adds fractional angles (5⁄2…) — same
mirrors, a triangle that wraps the sphere d>1 times → star tilings.
Flip on the pen and draw: each stroke folds into the fundamental domain,
so it reflects into every cell at once. Want lobes into space? → build.