comment: This is a theoretical draw. White has no winning plan because the king can't hide from the checks and the rook cannot be improved.
context: 1. c2c4 A natural opening move, but it's hard to say if it's better than the more restrained pawn advance to c3. 1.Nb3 and 1.d4 are good moves as well. 1... c7c6 This is more accurate than copying White's first move. 2. d2d4  2... h7h5 A difficult move. The idea is to play …g7-g6 without White having check on h6 and also move it to h4, restricting the development of White's queen on h1. But perhaps it would be better to fight for the center first. 3. c4c5  3... d7d5  4. h2h4 This is an important move sooner or later, in order to be able to play g3 and develop the queen. 4... e8f6  5. g2g3  5... g7g6  6. a1b3  6... f6g4 Carlsen complicates the game. The knight supports the …e7-e5 break and can go to h6 if attacked. 7. e1d3  7... c8f5  8. f2f3  8... g4h6 The bishop on f5 is in the knight's way and it's not easy to break on e5 anymore. One idea that Black has in mind is to capture the knight on d3 and play Nf5 next. 9. c1g5 A good development move. 9... a8c7  10. f1d1 In Freestyle chess you must always be alert to a surprising castling move. Keep this in mind. 10... c7e6  11. g5d2 The bishop has already fulfilled its function on g5 and it's time to flee from the knight. 11... f5d3 It's time to exchange the bishop to activate the knight on h6. 12. b1d3  12... h6f5 Attacking both d4 and g3. 13. e2e3  13... b7b6 This move allows White to maintain a big space advantage. 14. f3f4 Black is in trouble now, especially because of the precarious situation of the queen on h8. 14... f5h6 The knight repositions itself and frees the f6-square for the queen. 15. c1b1  15... h6g4  16. h1f3  16... h8f6 An important moment. 17. d1c1 This gives Black a tactical chance that Carlsen doesn't miss. 17... b6c5  18. b3c5  18... e6c5  19. c1c5  19... e7e5 This is the idea, exploiting the pin. 20. d4e5  20... b8e5 The right capture. 21. g1c1 This looks like a good and natural continuation, but after a series of difficult defensive moves, Black will find its way to a drawish endgame. 21... e5b2  22. c5c6  22... g4e5 A nice (and forced) tactical idea. 23. c6f6  23... e5f3  24. b1b2  24... f3d2  25. c1c7  25... f8g8 Without this surprising move Black would be completely lost. Now the position is equal. 26. f4f5 A good try, but Carlsen will find the way out. 26... d2e4 Another forced move. 27. d3e4  27... d5e4  28. f5g6  28... d8d2  29. b2c1  29... d2d3 Taking on a2 is also possible. 30. g6f7  30... g8g7  31. f6f4  31... d3e3  32. g3g4  32... h5g4  33. f4g4  33... g7f6  34. h4h5  34... e3f3  35. g4e4  35... f8f7  36. c7f7  36... f6f7 Even though the endgame is drawn and the defender is Carlsen, the greatest endgame player in history, let's not forget that rook endgames are notoriously difficult even for the brightest minds. 37. e4a4  37... f3c3 The computer indicates another drawing method: 38. c1d2  38... c3c7  39. a4a6  39... f7g7  40. d2d3  40... g7h7  41. a2a4  41... c7f7 During the game I felt the endgame was unpleasant, since Black's rook is passive. 42. d3e4  42... f7g7 A losing move. To understand why, first you should see the right defense after 43. e4d5 Missing a golden chance. 43... g7f7  44. a6e6 To be fair, the position is still very dangerous. 44... f7f4 Rook endgames are difficult. 45. a4a5  45... f4f5  46. e6e5  46... f5f6  47. e5e7 White goes for the wrong plan. 47... h7g8  48. e7a7 White could still go back with the rook and execute the plan analyzed before. 48... f6f5  49. d5c4 