Kids can transform, configure, and manipulate Block Builders for endless building and perpetual design. Fold and unfold the six distinctively hinged blocks to create skyscrapers, modern art sculptures, geometric marvels - just about anything imaginable. Includes 50 puzzle challenge cards. Block Builders puzzle challenge cards range from beginner to expert. Look at the design on the front of the card and recreate the shape using the indicated number of blocks. The solution is provided in an exploded view on the opposite side of the card.