Icosa lab — the 20-triangle world that inflates to a sphere

Author on the flat net (fold = 0): twenty equilateral triangles, cyan seams, red rings at the twelve sacrifice vertices. Fold it into the icosahedron, then inflate to a true sphere — the inflation is the only distortion step, and it is identical on every face: no poles, no ice-cap tax, no keg. Landmasses stay clear of seams and vertices by authoring inside faces.