A 3D shape with regular polygonal faces, meeting at equal angles, is a platonic solid. There are five platonic solids, the tetrahedron, cube, octahedron, dodecahedron and icosahedron. A prism is a ...

And shapes with more sides, like heptagons or octagons, can’t fit together to make the minimum three faces to make a corner. Therefore we can only make five Platonic solids. Image caption ...