1. e2e4  1... c7c5  2. g1f3  2... b8c6  3. d2d4  3... c5d4  4. f3d4  4... g8f6  5. b1c3  5... e7e5  6. d4b5  6... d7d6  7. c3d5 Since it was used in some games of the Carlsen-Caruana match, this move has become as important to opening theory as the old main line with 7.Bg5. 7... f6d5  8. e4d5 This is considered better than the alternative 8...Ne7. 8... c6b8  9. d1f3 A tactical and risky line. White wants to get the queen to c3 or a3, and the game becomes very direct, where the price of forgetting the analysis is very high. More on this shortly. 9... a7a6 It's a good idea to attack the knight immediately. 10. f3a3 The point of White's previous move. The knight is indirectly protected, thanks to the pin. Of course, Black always has the option of capturing the knight anyway and then playing to exploit his development advantage with the out-of-play white queen in the corner of the board. 10... f8e7 Time to finish development. 11. c1d2 Firouzja probably got his analysis mixed up. 11... e8g8  12. d2b4 This makes things even worse. 12... a6b5 This typical exchange sac gives Black overwhelming compensation. 13. a3a8  13... b8a6  14. b4d2  14... e7g5 With the king in the middle of the board and the queen out of play and with a chance of being trapped, White's position is already very dangerous. 15. d2g5 After another mistake, White has no chance of saving the game. 15... d8g5 Interestingly, all of this had already been played in a high-level game. 16. a8a7  16... a6b4  17. e1d1 A sad necessity: there's no other way to defend the pawn. 17... c8g4 A precise move, forcing White to weaken the e3-square. 18. f2f3  18... g4f5 With e3 ready for Black's knight, the attack is decisive. 19. c2c3 Only this is a new move. 19... b4c2  20. a1c1  20... c2e3  21. d1e2  21... e3c4 