And the final blunder.
1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. g2g3  3... d7d5  4. f1g2  4... d5c4  5. g1f3  5... c7c5  6. e1g1  6... b8c6  7. d1a4  7... c8d7  8. a4c4  8... b7b5  9. c4d3  9... c5c4  10. d3d1  10... a8c8  11. c1f4 Arjun is full of original ideas, but today it is his opponent to demonstrate one. This move is currently scoring better than 11.Re1. 11... f8e7 The main line. 12. b1c3  12... a7a6  13. a2a3  13... c6a5  14. d1c2  14... f6d5 [%c_effect d5;square;d5;type;Interesting;persistent;true] Santos is the first one to deviate from the trodden path. 15. c3d5  15... e6d5 Black has stabilized the center. If he manages to castle, his queenside majority will become a long-term asset. But since White has a temporary development advantage... 16. e2e4 [%c_effect e4;square;e4;type;GreatFind;persistent;true] is needed. Santos stabilizes the center further with 16... d7e6  17. f1e1  17... a5c6 and misses his chance to castle $1 18. e4d5 [%c_effect d5;square;d5;type;GreatFind;persistent;true] Now White opens up the game in his favor. 18... e6d5  19. c2f5 [%c_effect f5;square;f5;type;GreatFind;persistent;true] Arjun prevents his opponent from castling. 19... g7g6 Not the most desirable move, but what else $2 20. e1e7 [%c_effect e7;square;e7;type;Brilliant;persistent;true] Arjun has a strong sense for the initiative and seizes the chance $1 20... c6e7  21. f5f6  21... h8f8  22. f6a6 For a minuscule prize, White has kept the enemy king in the middle and is ready to shift his reserves toward it. 22... f7f6 [%c_effect f6;square;f6;type;GreatFind;persistent;true] The only chance. Black needs to castle by hand ASAP. 23. a1e1  23... f8f7  24. a6b5 As often happens, the most obvious move is not the best. Arjun throws away all his positional advantage for just one pawn. 24... e8f8 [%c_effect f8;square;f8;type;GreatFind;persistent;true] Now Santos' position is even easier to play. More importantly, the psychological switch from an attack to defense is extremely difficult, even for a talent like Arjun. 25. h2h4  25... f8g8  26. b5a4  26... e7f5  27. e1d1  27... d8d7 [%c_effect d7;square;d7;type;Interesting;persistent;true] Not bad at all. 28. a4c2  28... f7e7 [%c_effect e7;square;e7;type;GreatFind;persistent;true] 29. c2c3  29... c8e8  30. f3e1 This does not work due to a concrete reason. 30... d5g2 This lets a good amount of the advantage slip away. 31. e1g2  31... d7d5  32. f4c1 White errs in return. 32... f5d6  33. g2f4  33... d5f5 With the inevitable break g6-g5 $1 34. d4d5  34... g6g5 [%c_effect g5;square;g5;type;GreatFind;persistent;true] 35. h4g5  35... f6g5  36. f4e6  36... h7h6  37. c3d4  37... e7f7 