Abstract: A set of elements have square surfaces with patterns thereon, the elements being arrangeable such that the square surfaces are juxtaposed to form a design. The patterns are defined by one or two contour lines on the square surface, the surface areas on either side of each contour being different colors. The square surfaces have patterns belonging to two groups or have no pattern thereon. The first group includes square surfaces having only circular arcs as contour lines and the second group includes square surfaces having only straight lines as contour lines. The first group includes four types and the second group includes two types.