Convolution is composed of seven polycube pieces: Six of these are made up of nine cubes (each): The seventh has ten. Sixty-four is (of course) four cubed. Taking the puzzle apart and putting it back together is strictly sequential. Each piece is locked firmly in place, its movement constrained by the other pieces and not infrequently by one's fingers.

There is a surprise in the puzzle design: One of the pieces requires rotation as well as orthogonal pushing and pulling. This rotation is accomplished only by rounding two edges of the puzzle's component cubes slightly, rendering the pieces of which those cubes are a part not proper polycubes. I feel this perceived flaw just adds to the puzzle's overwhelming charm.

According to this website, Stewart Coffin made fifty of these puzzles in the early eighties. Last month, someone paid over $1200 U.S. for one of them! (I seriously need to locate all my Stewart Coffin original boxes and information sheets.) There was a time when I could both disassemble and reassemble Convolution using only my bare feet.