Credit: Gautam Agarwal, UC Berkeley Fans of Candy Crush Saga, Flow Free or Minesweeper should check out a challenging new mobile game app, hexxed, that will stretch your brain as it helps brain researchers understand human strategic thinking and perhaps improve the reasoning of artificial intelligence. The puzzle game was released this month through Apple's App Store and Google Play by neuroscientist Gautam Agarwal and colleagues at the University of California, Berkeley, and by Champalimaud Centre for the Unknown in Lisbon, Portugal. Those who download hexxed will confront a game more challenging than most phone-based games, which can be played mindlessly while killing time or watching TV. Those playing hexxed must learn how to succeed with almost no instructions -- they have to figure out the rules on the fly.