1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g1f3  3... d7d5  4. g2g3 The Catalan has become a powerful weapon for Nepomniachtchi. After all the work he had to do in order to play it with Black in the match against Carlsen, no wonder he decided to try it with the other color. 4... f8b4 This check is one of the most reliable options for Black. 5. c1d2  5... b4e7  6. f1g2  6... e8g8  7. e1g1  7... b8d7 The point is that the bishop is not well placed on d2 in the lines where Black refrains from taking on c4. With the bishop on c1, White can play b3-Bb2 or Qc2-Nbd2, plans that are not available now. 8. d1c2  8... c7c6  9. h2h4 This incredible idea is only White's 16th most popular choice in this position $1 This shows that it's still possible to find fresh ideas even in the most studied openings. But what's the idea of this mysterious move $2 From what I understand, the reasoning is this: 9.Nc3 is premature because Black can take the c4-pawn and then defend it with b7-b5. That's why White makes an useful move and intends to answer 9...b6 (the most natural move) with 10.Nc3. If Black captures the c4-pawn and plays b6-b5 in this case, then White has an extra tempo and the pawn is quite useful on h4. 9... b7b6  10. b1c3 This is the point. The pawn is useful on h4 in case Black now decides to take on c4. 10... c8a6  11. c4d5  11... c6d5  12. f1c1  12... a6b7 A new move. 13. d2f4  13... a8c8  14. c2b3  14... a7a6  15. a2a4 Preventing the typical move b5 that gives Black more space on the queenside. 15... h7h6 A useful move, giving some air to the king and taking the g5-square from the white pieces. 16. e2e3 This is a very difficult move to play, but this pawn on e3 will be very helpful for White in a few moves. The problem is that the f4-bishop doesn't have many squares now; it must be ready to be sacrificed in some variations. 16... f6h5 It's curious that all moves with this knight are possible and good. Actually this one is my least favorite. The capture on f4 helps White because after he takes with the e-pawn, he gets more space and a clear plan of action. 17. g2h3  17... c8c4  18. b3d1 Now g5 is avoided because the h5-knight is hanging. 18... h5f4  19. e3f4 The pawn structure is now favorable for White. Black has no pawn breaks and is suffocated without an active plan. 19... e7d6  20. h3f1 Improving the bishop. 20... c4c7  21. f1d3  21... d7f6  22. d1e2  22... d8a8  23. f3e5  23... f8c8  24. f2f3 A solid move, taking the e4-square from Black's knight. White's is plan is to attack on the kingside with g4-g5 and so on. Black is helpless against this plan and should seek some desperate counterplay. Notice the awkward placement of the queen on a8, far away from the action. This piece would be much better placed on e7. 24... h6h5  25. e2e3  25... d6b4  26. c1c2 Nepomniachtchi plays very carefully, reinforcing the position before going for the attack. 26... g7g6  27. a1c1  27... g8g7  28. d3g6 A flashy move, well in Nepomniachtchi's style. He has great feeling for the initiative. Both 28.g4 and even 28.f5 are also good.