21 Cube Dissection Puzzles

Here are 21 different puzzles based on the dissection of a 64 unit cube into 4 parts. Six pairs of pieces are given. To make a puzzle choose any two pairs; the 4 puzzle pieces are to be assembled into a cube. The choices include using the same pair twice for a total of 21 possible puzzles. The puzzles are of four types: four where all 4 pieces are identical, eight where the pieces are of two types, eight where the pieces are of three types, and one where all four pieces are different. To get the puzzle with all different pieces choose the pair pieces_1_and_2.stl and the pair pieces_3_and_4.stl. OpenSCAD code is included.