1. g1f3  1... d7d5  2. g2g3  2... g8f6  3. f1g2  3... e7e6  4. e1g1  4... f8e7  5. d2d3 Nepomniachtchi chose the  King's Indian Attack for the decisive game. 5... e8g8  6. b1d2  6... c7c5  7. e2e4  7... b8c6 This can be considered Black's main line. 8. f1e1  8... b7b5  9. e4e5  9... f6d7  10. d2f1  10... a7a5  11. h2h4 Those of you who followed my mini-course on Chess.com about the KIA are familiar with the ideas for both sides. White is quickly  building a strong attacking setup on the kingside while maneuvering his  queenside knight to g4, whereas Black tries to counter on the opposite  wing and the center. 11... b5b4  12. c1f4  12... a5a4  13. a2a3 An important move for  White, who needs to slow his opponent down on the queenside. 13... b4a3  14. b2a3  14... a8b8  15. f1e3 The knight can reach the g4-square from here too. 15... c8b7 An obvious developing move and a novelty. 16. c2c4 Nepomniachtchi fires back at the center while opening the road for his queen. 16... d7b6  17. c4d5  17... b6d5 However, So keeps playing  confidently and is not afraid to sacrifice a pawn. 18. d1a4  18... d5c3 Playing for activity. 19. a4c4 