Chess opening are so complex and theoretical that amateur players will have trouble understanding them. 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 does Pedro Damiano (1512), and Ruy López de
Ruy Lopez Morphy, and it is named for him. Steinitz did not approve of the move; in 1889, he wrote, "on principle this ought to be disadvantageous as it drives the bishop where it wants to go". Steinitz's opinion did not prevail, however; today, 3...a6 is played in over 65 percent of all games beginning with the Ruy Lopez. After 3...a6, the most commonly played line is the Closed Defence, which goes 4.Ba4 Nf6 5.0-0 Be7, discussed in the two following sections. Alternatives to the Closed Defence described in this section are: In the Exchange Variation, 4.Bxc6, ("ECO" C68–C69) White damages Black's