Google’s artificial intelligence just smashed through another barrier. The company’s DeepMind software beat professional Go player Lee Se-dol, currently ranked second best in the world, in the first of five matches pitting man against machine.

The match lasted almost three and a half hours before Lee eventually admitted defeat. Afterwards, he told the press that he was expecting a victory. “I was very surprised,” he said (via The Verge). “I didn’t expect to lose. I didn’t think AlphaGo would play the game in such a perfect manner.”

Lee is also optimistic that he can beat DeepMind in the next match. He noted that Google’s AI had a surprisingly strong opening, and caught him off guard with a few moves throughout the game. The pair will face off again this Saturday, followed by games on Sunday and Tuesday in an eventual five-match series.

If DeepMind can claim victory, it will be a huge moment for artificial intelligence, but even this single win is a big deal. Go has always been one of the final benchmarks for artificial intelligence, due to the high level of strategy and nearly infinite possibilities. Beating a top-ranked player is huge.