1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... d7d5 The Queen's Gambit is an essential guest at world championships, with memorable games in the legendary clashes between Capablanca vs. Alekhine, Spassky vs. Fischer, and Karpov vs. Kasparov, among others. 4. c4d5 The exchange variation was Kasparov's favorite. 4... e6d5  5. c1g5  5... c7c6  6. e2e3  6... h7h6 In the 90s, moving the h-pawn in the Exchange Orthodox positions like this was considered an opening mistake. This is one of the clearest changes in theory in recent years. The computer showed that it's OK to play like this and also started to indicate more active plans for Black, like advancing the queenside pawns with b7-b5 and a7-a5, which was also considered anti-positional. 7. g5h4  7... f8e7  8. f1d3  8... e8g8 Ding has some experience in this position, so it didn't come as a surprise to Nepomniachtchi. Two of the Chinese GM's opponents decided not to put the queen on c2 so quickly, but he had no trouble equalizing in those games. 9. d1c2 