comment: A blunder that loses the game.
context: 1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. d1c2 The Capablanca Variation against the Nimzo-Indian is solid and reliable, making it an especially good weapon if White only needs a draw. 4... d7d6  5. g1f3  5... b8d7  6. e2e3 A good way of developing. There are alternatives-White is usually slightly better. 6... b7b6  7. f1e2  7... c8b7  8. e1g1  8... b4c3 This move is necessary after White has castled, since the knight isn't pinned anymore and is ready to move, leaving the b4-bishop in danger. 9. c2c3  9... f6e4 Carlsen needed a win and embarks on a dangerous enterprise. 10. c3c2  10... f7f5 A natural continuation of the previous move, although it's better to castle. 11. d4d5 This move is seen in positions similar to this one and originating from the Bogo-Indian Defense. The central advance throws cold water on any claims Black has on the kingside. Capturing leads to catastrophe (as will happen in the game), but closing the center with e6-e5 leaves Black with no prospects and a terrible bishop on b7. 11... e6d5  12. f3d4 Black is full of weaknesses and the king is still in the middle of the board. The f5-pawn is attacked and the knight can also go to e6. 12... d5c4 This makes things even worse, but it's hard to recommend anything. 13. d4e6  13... d8c8 Black's position is sad and I guess even die-hard Carlsen fans didn't expect a turnaround at this point. 14. f2f3 Many roads lead to Rome. 14... e8e7  15. e6g7  15... c8f8  16. g7h5  16... e4c5  17. c2c4 White has plenty of winning moves. 17... d7e5  18. c4h4  18... e7d7  19. b2b4  19... c5e6  20. c1b2  20... f8e7 Amazingly Black's best option is to go for an endgame an exchange down. 21. h4e7  21... d7e7  22. f3f4  22... h8g8  23. h5g3  23... g8g3 Otherwise the f5-pawn is captured with check. 24. h2g3  24... e5g4  25. e2g4  25... f5g4 Black doesn't have even a pawn in exchange for his troubles, but miracles happen in speed games. 26. f4f5 Of course not the only way, but good enough. 26... e6g5  27. b4b5 Fixing the pawn on c7. 27... a7a6  28. a2a4  28... g5e4  29. a4a5 An interesting move, although not really necessary. 29... e4g3  30. f1e1  30... b6a5 White's win is no longer certain, although So needed only a draw. 31. f5f6  31... e7e6  32. a1a5  32... a6b5  33. a5b5  33... b7e4 Here White needs to be very precise. 34. e1a1  34... a8c8  35. b5g5  35... h7h5  36. g5g7  36... g3f5  37. g7h7  37... c8b8  38. b2c3  38... c7c5  39. g1h2  39... h5h4  40. a1a7  40... h4h3 Carlsen is quick to spot a golden chance to create a mating net. 41. h7e7  41... e6d5 