Chess

Chess in Code Geass seems to follow from the same basic rules, objective and design as Chess in the real world. Chess seems to play an important Role in Britannian Nobility as a way of developing and demonstrating tactical skill. Chess was rarely shown in the series, only appearing in order to show Lelouch's considerable intellect or, later, to show that Schneizel's strategic prowess was equal to that of Lelouch. Chess is a form of gambling, which Lelouch is a master of and with an infamous reputation. Depending on the situation Lelouch would alternate between offering his services as an aide for other chess players to taking part in actual games himself. Lelouch himself is a masterful player, having previously lost only to Mao, as a result of his Geass allowing him to read and pre-empt Lelouch's moves, and Schneizel, due to the former's considerable talent at strategy and subtle manipulation. Lelouch preferred an aggressive style, counting on surprise and complete shock on the part of his enemies, usually by aggressive use of his king, a move that normally would be a very poor choice in the actual game, this often led him to quote "If the king does not move, his subordinates will not follow," effectively demonstrating his own feelings toward command. This was often used as a motif and comedic foil referencing the king's ability for limited movement, whilst allowing a comment on Lelouch's poor physical ability. Lelouch was also known to cut class during school days in order to play chess to supplement his income and as an attempt to fight his considerable boredom as he sought for a "more challenging opponent."

For more information including rules and history, see the wikipedia article of the actual game of Chess

List of known Chess matches in Code Geass anime

 * Lelouch's employer (Black) vs Unknown Nobleman (White). Result: inconclusive (replaced by Lelouch). Appearance: Episode 1 Season 1
 * Lelouch (Black) vs Unknown Nobleman (White). continuing from the first one. result: Victory for Lelouch. appearance: episode 1 season 1.
 * Lelouch (Black) vs Mao (White). result: Victory (checkmate?) for Mao. appearance: episode 14 season 1.
 * Lelouch (Black) vs Mao (White). result: Victory (check) for Mao. appearance: episode 16 season 1.
 * Lelouch (White) vs "the Black King" (Black). result: Victory for Lelouch. appearance: episode 1 season 2.
 * Lelouch (Black) vs Schneizel (White). result: Inconclusive (threefold repetition), disturbed by Nina Einstein. appearance: episode 9 season 2.

List of known Chess Players
Holy Empire of Britannia. Chinese Federation.
 * Lelouch Lamperouge/Lelouch vi Britannia.
 * Clovis la Britannia.
 * Schneizel el Britannia.
 * Charles zi Britannia.
 * Mao