zealouspawn: A key point in this endgame is white's 72nd move. Instead of the game text he can choose to liquidate into a King and Pawn endgame that I initially thought looked drawing:
72 Rxg4 Rxg3+ 73 Rxg3 hxg3 74 Kxg3, all of which is more or less forced. Then I spotted..
74.. Kg7! and black has "distant opposition", a good king and pawn concept to understand. Here anything white tries loses:
75. Kg4 Kg6 76. Kf4 Kh5 77. Kf3 Kg5 78. Ke4 Kg4 79. Ke3 Kf5 80. Kd4 Kf4
and at long last the white king is bullied off the spot for an easy win. Non-obviously, other white tries transpose to this line.
75. Kf4 Kh6 76. Kg4 Kg6 (transposing) or 76. Ke4 Kg5
75. Kh4 Kh6 is much the same
Or white can try to hang back with:
75. Kf3 Kh6! (avoiding 75.. Kg6 76 Kg4, allowing white to steal the opposition and deny the black king) 76. Kf4 Kh5 and once again the pawn becomes undefendable