Human–computer chess matches computer Deep Thought in an exhibition match. Deep Thought, however, was still considerably below World Championship Level, as the then reigning world chess champion Garry Kasparov demonstrated in two convincing wins in 1989. The "Chess Genius" program was entered into a Professional Chess Association rapid chess tournament in 1994. It defeated and eliminated world champion Kasparov, but lost to Viswanathan Anand in the next round. This was the first time a computer had defeated the world champion in an official game, albeit at rapid time controls. Kasparov played a six-game match against IBM's Deep Blue in 1996. Kasparov lost the
Reversi game has been particularly attractive to programmers. Therefore, the best Othello computer programs have easily defeated the best humans since 1980, when the program "The Moor" beat the reigning world champion. In 1997, Logistello defeated the human champion Takeshi Murakami with a score of 6–0. Analysts have estimated the number of legal positions in Othello is at most 10, and it has a game-tree complexity of approximately 10. Mathematically, Othello still remains unsolved. Experts have not absolutely resolved what the outcome of a game will be where both sides use perfect play. However, analysis of thousands of high quality games