A computer defeated China's top player of the ancient board game "GO" today, earning praise that it might have finally surpassed human abilities in one of the last games machines have yet to dominate.<br/><br/>Google's AlphaGo won the first of three planned games this week against Ke Jie, a 19-year-old prodigy, in Shanghai. The computer will also face other top-ranked Chinese players during the five-day event.<br/><br/>AlphaGo beat Ke by a half-point, "the closest margin possible," according to Demis Hassabis, founder of DeepMind, the Google-owned company in London that developed AlphaGo.<br/><br/>AlphaGo has improved markedly since it defeated South Korea's top competitor last year and is a "completely different player," Ke told reporters.<br/><br/>Go players take turns putting white or black stones on a rectangular grid with 361 intersections, trying to capture territory and each other's pieces by surrounding them.<br/><br/>The game, which originated in China more than 25 centuries ago, has avoided mastery by computers even as they surpassed humans in most other games. They conquered chess in 1997 when IBM Corp's Deep Blue system defeated champion Garry Kasparov.<br/><br/>Go, known as weiqi in China and baduk in Korea, is considered more challenging because the near-infinite number of possible positions requires intuition and flexibility.