Poker is a powerful combination of strategy and intuition, something that’s made it the most iconic of card games and devilishly difficult for machines to master. Now an AI built by Facebook and Carnegie Mellon University has managed to beat top professionals in a multiplayer version of the game for the first time.

Games have proven a popular test-bed for AI in recent years, and when Google’s AlphaGo cracked the ancient Chinese board game Go it was a watershed moment for the field. But most of the games AI has been tested on have been so-called “perfect information” games.

As complex as Go is, you can see where all your opponent’s pieces are, and it’s theoretically possible to map out every possible future sequence of moves based on the current configuration of pieces on the board. In poker your opponent’s hand remains hidden, which makes it much harder.