I left chess in 2012. I did not touch it for several years. Then I decided to test my strength in Internet blitz. I started from scratch. The board floated before my eyes, and my knee twitched. Less than two months later, I crossed the grandmaster rating mark. My opponents, among them lots of players with a big name, played chess better than me. Surprisingly though, I knew more. On a small island of chess theory, onto which I lured them, I was better equipped. Much better! About 30% of the games ended in wins around the 20th move. A quarter of the games simply ended in mate. In all games, I...