This was Nakamura's idea. It seems as Black  is mating.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1c4 The evergreen Italian. 3... f8c5  4. e1g1  4... g8f6  5. d2d3  5... d7d6  6. c2c3  6... h7h6  7. f1e1  7... e8g8  8. b1d2  8... a7a5  9. d2f1  9... c8e6  10. c4b5 All of this is very popular nowadays and the players  actually had an earlier discussion in the line. 10... c6e7  11. d3d4  11... e5d4  12. c3d4  12... c5b6  13. f1g3  13... d6d5  14. e4e5  14... f6e4 Now the game resembles the Ruy Lopez.  Carlsen deviates from their earlier game with... 15. b5d3 ...which is the right diagonal for his bishop. 15... e4g3  16. h2g3  16... a5a4 Now the bishop retreats with tempo. 17. d3c2  17... a4a3  18. b2a3 Carlsen took some time on this move and then chopped the pawn  off. 18... e6g4  19. a3a4 An excellent idea. First White brings the dark-squared bishop  in the game. 19... d8d7  20. c1a3  20... f8e8 Finally Nakamura is ready for Bg4-f5, but... 21. a3e7 An excellent positional operation which secures White a  long-term advantage. Both the light squares complex and Black's kingside  are in jeopardy. 21... d7e7  22. d1d3  22... g7g6  23. f3h4 Now the sacrifice on g6 seems inevitable. After a long thought Nakamura bets on activity. 23... e7b4  24. h4g6  24... b4d4 The point. But now there is 25. g6e7  25... g8f8  26. e7d5 It seems like Black is almost done, but Nakamura has an  ingenious idea on his mind. 26... d4f2 "Just a shock. I just  didn't believe it was possible." (Carlsen) 27. g1h2 '"And then, when he went..."' 27... a8d8 "...my first thought was: I may have missed some kind of mate. But it turns out he is lost,  fortunately." 28. e1f1 