The letter L may be tessellated in a variety of ways, as seen by the number of sites dedicated to it. This book's tessellation designs are all upper-case letters. Lower-case letters tessellate as well, and some of their conceivable forms are shown in the typeface selected for this introduction. A lower-case l is identical in every way to an uppercase L, except that it does not need to be filled. Upper-case Ls are used in logos and other graphic design work because they make excellent shapes that catch the eye. They have two equal sides and two equal angles, so they are symmetrical. When you see an upper-case L, you should think symmetry! Lower-case l's are used when strict symmetry isn't necessary, such as with drawings or handwritten notes. They have three equal sides and one unequal angle, so they're asymmetrical. This makes them unique, interesting, and attractive. There are eight different ways letters can tessellate: AAA, BBB, CCC, DDD, EEE, FFF, GGG. There are also four ways spaces can tessellate: AAA, BBB, OOO, and VVV. Finally, there are three combinations: AAO, BBO, and COG. That's 10 total combinations. If you include rotated versions of these patterns, there are actually 11 total.