Se-dol and Hong Chang-sik during the 2003 KAT cup. This game is notable for Lee's use of a broken ladder formation. Normally playing out a broken ladder is a bad mistake, a pitfall associated with bad beginner play; the chasing stones are left appallingly weak. Between experts it should be decisive, leading to a lost game. Lee, playing black, defied the conventional wisdom, pushing development of the ladder to capture a large group of Hong's stones in the lower-right side of the board. Although Black could not capture the stones in the ladder, White ultimately resigned. AlphaGo vs Fan Hui In October 2015, the computer program AlphaGo became the first artificial intelligence program to defeat a professional Go player on a full size board and on equal terms (without handicap), when it won 5–0 against 2 dan European Champion Fan Hui. The news was announced on 27 January 2016 in order to allow publication of a scientific paper describing the algorithms used for AlphaGo. The victory gained very wide attention since this was a landmark not believed accessible to current technology, given the complexity and intuitive nature of the game, and its lack of suitability for conventional tree searches and position-evaluation based methods which had led to success in games such as chess. However it was generally believed that AlphaGo, while remarkable for a computer player, had made mistakes and would probably be unable to hold its own against a world-ranking player. AlphaGo vs Lee Sedol Five months after defeating Fan Hui, AlphaGo played a series of five matches against 9 dan Lee Sedol, a South Korean professional widely considered one of the strongest and most creative players in the world. Prior to the game, in February 2016, Lee Sedol expressed confidence in winning, although acknowledging AlphaGo as a "strong player", and discussion on website GoGameGuru reported that at the time that "the majority of the world’s top players had thought [AlphaGo winning a game against Lee] to be practically impossible". The game conditions were: Chinese rules, komi (compensation points for playing second) of 7.5, 2 hours time and three 60-second byoyomi (limited time after their initial time is used). As with its previous games against Fan Hui, the tournament was on a full size board and on an equal basis. The computer won the first three games of five, Lee won the fourth, and the computer won the fifth