Computers have already beaten the world’s best humans at classic games like chess and Go.

Now one has beaten one of the world’s best players of the smash-hit video game “Dota 2.”

Live on stage at The International, developer Valve’s flagship $24 million tournament, a bot from Open AI defeated professional gamer Danylo “Dendi” Ishutin in a surprise, previously unannounced one-on-one exhibition matchup. The bot from OpenAI, the $1 billion artificial-intelligence research nonprofit cochaired by Tesla Motors CEO Musk and Y Combinator President Sam Altman, beat Dendi in the first match in about ten minutes; Dendi resigned from the second match, and declined to play a third.

Watch the match here:

“Please, stop bullying me,” Dendi, who’s estimated to have earned $735,449.40 in winnings in his career, said to the bot during the match.

Elon Musk himself took to Twitter to praise OpenAI for its achievement, saying its bot was the “first ever to defeat world’s best players in competitive eSports.”

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OpenAI first ever to defeat world's best players in competitive eSports. Vastly more complex than traditional board games like chess & Go. — Elon Musk (@elonmusk) August 12, 2017

In a video ahead of the matchup, OpenAI CTO Greg Brockman explained that the company’s special bot was trained by playing a “thousand lifetimes” of matches against itself, with “coaching” from the company. Brockman also boasted that the bot had already bested several pro “Dota 2” players.

“Over the past week, our bot was undefeated against many top professionals including SumaiL (top 1v1 player in the world) and Arteezy (top overall player in the world),” wrote Brockman in a blog entry discussing the bot.

The idea of “self-playing” is key to the advances that OpenAI is pushing for, Brockman told Business Insider following the match. It’s a useful way for an AI system to learn even the most complex tasks. It doesn’t learn anything if it goes up against either a weaker player or a far stronger one. By playing itself, it always has a worthy opponent, he said.

“You kind of see this AI go from total randomness” into the game-winning system we saw here, Brockman said.

You can watch OpenAI’s introductory video here:

Artificial intelligence companies have a history of using video games to test their technology: Google’s DeepMind has tackled “StarCraft 2,” while a Microsoft AI team recently claimed to attain the high score in Ms. Pac-Man.

OpenAI isn’t just walking away after its victory. The organization hopes to have its bot ready to play in a proper five-on-five match next year.

“‘Dota’ is not solved,” Brockman told Business Insider.

Still, he expects OpenAI will explore using the same bot to play other games. The same “self-playing” principles it uses can be applied almost anywhere, he said. And OpenAI is excited to see what it can learn under a variety of circumstances.

“At OpenAI, we’re not just about publishing a paper,” Brockman said. “It’s really about building working systems and doing something that would have been impossible before.”