An artificial intelligence can now play the real-time strategy video game StarCraft II so well that it is better than 99.8 per cent of human players. The AI, called AlphaStar, was developed by tech firm DeepMind, which is owned by the same parent company as Google. AlphaStar played anonymously against human players in a series of online games on the official StarCraft II game server, Battle.net, and ended up ranked in the top 200 players for each of the leagues it competed in. StarCraft II is a popular science-fiction game that involves controlling armies and building infrastructure. Players must compromise between short-term payoffs and long-term gain.

In December, AlphaStar played as a Protoss and won five games against Dario Wünsch, a German player who goes by the gamer handle TLO and who also played as a Protoss (although it is not the group in which he specializes). A week later, the AI won five games again, this time against a tougher Protoss competitor: Grzegorz Komincz, a professional gamer from Poland who goes by the name MaNa. DeepMind announced the victories Thursday during a live stream on YouTube and Twitch. The researchers used a sort of tournament-style approach to train AlphaStar. First, they spent three days training a neural network -- a machine-learning algorithm modeled after the way neurons work in a brain -- on replays of human players' StarCraft II games. This neural network was used to create a number of computer-based competitors that played many, many rounds of the game against each other, learning from their experiences, over the course of two weeks.