GoKawiilGreg Egan explains construction of Steffen's flexible 14-face polyhedron
Greg Egan's write-up details how Klaus Steffen built a flexible polyhedron from 14 triangular faces that can change shape while every face keeps its exact dimensions. The explanation walks through assembling a four-triangle pyramid with a non-planar quadrilateral base, then attaching further triangles whose vertex positions are fixed by existing edges, producing a shape with one degree of freedom overall.