Best.
1. c2c4  1... e7e5  2. b1c3  2... g8f6  3. e2e3  3... d7d5  4. c4d5  4... f6d5  5. g1f3  5... b8c6  6. d1c2 It is curious that a year ago in a similar must-win situation, Carlsen chose the same opening against Nakamura to try and level the score. For several moves, the two players followed that game. 6... d5b4  7. c2b1  7... f7f5  8. a2a3  8... b4d5  9. d2d3  9... c8e6  10. f1e2  10... f8e7  11. e1g1  11... e8g8  12. c3d5  12... e6d5  13. b2b4  13... a7a6  14. c1b2  14... e7d6 [#] 15. b2c3 The novelty! Artemiev prepares b4-b5. 15... d8e7 Ignoring the threat. 16. b4b5  16... a6b5 Black sacrifices the pawn hoping to get it back quickly on the a-file. 17. b1b5  17... d5f7  18. b5b7  18... c6a5  19. b7b2 And Nakamura sank into thought, probably realizing that he had missed a few details in his preliminary calculations. 19... f8b8  20. b2c2  20... a5b3 