"Caco Puzzle Blocks" is a modular toy encouraging children to create countless polyhedrons easily. It is foldable, connectable using only one kind of material, polypropylene(PP) plastic. There are 4 kinds of round sheets as the basic modules in this system. Each piece has circle-inscribed regular polygon tracks on both sides. And the regular polygons have same side length. With the 4 kinds of blocks, kids can combine several pieces together to create various forms such as balls, containers, buildings. Also, because of the flexible of the PP material, some unclosed form is changeable and transformable. Children will be amazed by the unexpected shapes which are transformed from their original works. "Caco Puzzle Blocks" helps children to cognize 3D space, and have fun imaging and developing their own minds.