 An example is the Perenyi Attack of the Sicilian Defense (see diagram), which yields an immensely complicated and tactical position that even strong players have difficulty handling, and that is beyond the comprehension of most amateurs.Major changes in the rules of chess in the late fifteenth century increased the speed of the game, consequently emphasizing the importance of opening study.Thus, early chess books, such as the 1497 text of Luis Ramirez de Lucena, present opening analysis, as do Pedro Damiano (1512), and Ruy López de Segura (1561).