3D Building Block Puzzle — 12 Pieces, 80 Challenges

Twelve coloured cubes stay threaded on an inner cord. They fold and turn the chain — they do not pull it apart — until it matches the card.

Forty double-sided cards make eighty challenges across four levels. Folded, the chain is about 8 × 6 × 2 cm. Forcing the cord will spoil the puzzle.