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
Comparison of Portuguese and Spanish in both languages, but the stress falls on different syllables: Although the vocabularies of Spanish and Portuguese are similar, the two languages differ phonologically from each other, very likely because of the stronger Celtic substratum in Portuguese. Phonetically Portuguese bears similarities to French and to Catalan while the phonetics of Spanish are more comparable to those of Sardinian and Sicilian. Portuguese has a significantly larger phonemic inventory than Spanish. This may partially explain why it is generally not very intelligible to Spanish speakers despite the lexical similarity between the two languages. One of the main differences between the Spanish and