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 C64), 3...Bc5, is possibly the oldest defence to the Ruy Lopez, and has been played occasionally by former world champion Boris Spassky and Boris Gulko. White's most common reply is 4.c3, when Black may choose to play 4...f5, the Cordel Gambit, leading to sharp play, after which 5.d4 is considered the strongest reply. More solid for Black is instead, 4...Nf6, when 5.0-0 0-0 6.d4 Bb6 leads to the Benelux Variation. White's principal alternative to 4.c3 is 4.0-0, when Black can transpose to the Classical Berlin with 4...Nf6 or play 4...Nd4 which isn't so bad for Black. An alternative for White