Everybody loves deltahedra! That is, a 3-D solid whose faces are all equilateral triangles. A strictly convex deltahedron is one whose edges always curve inward (i.e. they are round; as opposed to concave where they curve outwards). Strictly convex means that no two faces can be coplanar.
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"We have the tetrahedron, the cube, the octahedron to the dodecahedron and icosahedron cuz of you!"