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
Tactical decision game Lieutenant?", the games in the "Tactical Problems ..." series were based them on descriptions of actual engagements that took place between 1914 and 1953. Some of these were first-hand accounts written by S.L.A. Marshall, Erwin Rommel,and Friedrich von Mellenthin. Others were secondary works composed by military historians.) Regardless of the actual events that inspired them, all of the problems were modified to reflect the organization and equipment of the 1980s. Thus, none of these historically-inspired games can be classified as decision-forcing cases.) Tactical decision game A tactical decision game is a decision game that puts students in the role of