These ancient Chinese puzzles have fascinated mathematicians for centuries. Their geometrical proportions and infinite possibilities have made them useful for practices in logical thinking. Fu Tsiang Wang and Chuan-chin Hsiung mathematically proved in 1942 the existence of a finite set of patterns referred to as "convex". Meaning that there are no indentations along the outside edge and an inside line from any edge to any other edge will not go outside the edges of the design. There are only 13 silhouettes that qualify. Read more about the history of this remarkable puzzle as well as some of the possibilities it has here.