Hong Seok-Hyun (R), chairman of South Korea's Baduk Association, awards South Korean professional Go player Lee Sedol after Lee finished the final match of the Google DeepMind Challenge Match against Google's artificial intelligence program, AlphaGo, in Seoul, South Korea, March 15, 2016.

The 33-year-old kept a tight game with the two-year-old computer program by the middle of the match, but a decisive moment came past halfway as AlphaGo succeeded in attacking the lower-left side.

At the lower-left side, AlphaGo made questionable moves, which looked like blunders at the first sight, but those also proved to be a strategy to win more territory in hindsight.

Commentators said AlphaGo made excellent moves in the latter half of the game, proving its better capability to play as time goes on. Lee didn't make any big missteps during the game, experts said.