1. c2c4  1... e7e5  2. g2g3  2... c7c6  3. g1f3  3... e5e4  4. f3d4  4... d7d5  5. c4d5  5... d8d5  6. d4c2  6... g8f6  7. b1c3  7... d5e5  8. f1g2  8... b8a6  9. e1g1  9... f8e7  10. c2e3 Up to here, everything has been pretty well-known theory. Now, while Ian's next move is very natural, I think it is not best. 10... e8g8  11. a2a3 Simple, but strong. White plans b4, Bb2, and once Black's queen is destabilized, the e4-pawn can become a target. 11... f8e8  12. b2b4  12... f6g4 Black is playing very energetic chess, but at some point, bluffs need to be called. 13. c1b2  13... e5h5  14. h2h4 This seems to be asking for trouble. 14... e7f6  15. d1c2  15... g4e3  16. d2e3  16... c8f5 The machine still likes White's position here, provided he plays a couple of good moves. But, I really dislike the way the last few moves have gone for him. Now the e4-pawn will survive. As such, Black's kingside attack is much scarier and White's g2-bishop is stuck out of play. 17. c3a4 I did not love Ding's earlier decisions, but this was somewhat a matter of taste. I wanted to take the pawn. But this move is just a mistake. 17... f6b2  18. a4b2  18... a6c7  19. b2c4  19... e8e6 Now, Black has a very simple plan. Overprotect the e4-pawn to keep all of White's pieces from coming back to the kingside, and then at some moment, g5 will come and quickly end the game. White can probably hold the position together with extremely precise play, but even the world number-two was not up to the task. 20. f1d1  20... c7d5  21. d1d4 Now, here the machines claim that ...g5 won the game. I'm sure they are right... but does it matter? Nepo played it slower, but I don't really see this as some shortcoming on his part. 21... h7h6 Now, Black is ready for g5 next. If he is allowed to take on h4, the game is over. If White takes on g5, then …hxg5 will come, …Rh6 will follow, and the game is over too. My computer claims White can hold on here, and with more moves than one, but this is the kind of mistake that I think would have been completely ignored in the pre-computer era. 22. c2d2 This is way too slow, and a surprising mistake from a player of Ding's caliber. You need to activate all the pieces. 22... a8e8 Black overprotects e4 hard, and now g5 is coming. White is crushed. 23. g1h2  23... f5g4  24. c4a5 