“Talking about parallelepipeds’ value: In geometry, a parallelepiped is a three-dimensional figure formed by six parallelograms (the term rhomboid is also sometimes used with this meaning). By analogy, it relates to a parallelogram just as a cube relates to a square or as a cuboid to a rectangle. In Euclidean geometry, its definition encompasses all four concepts: parallelepiped, parallelogram, cube, and square.
So what I made was simple: copy the whole design and mirror it with a thicker line to turn the two pasted layers into a three-dimensional view.” via FANTASARAXIA page.