fredthebear: The champ gets surprised in a simultaneous exhibition game. Hey, it happens once in awhile. Kasparov is playing a master-level opponent who defends well. This game features hanging knights and a shunned kingside attack.
Via the Slav defense, Black opens in a Dutch Stonewall, Be7 Classical variation. He gets a good game despite having an isolated queen pawn, which generates more operational space (especially laterally along the 6th and 7th ranks) than a typical Stonewall. The Black queen's rook becomes more useful (with lift) early in the game as a result.
Black's king knight performs with great accuracy in this game. White plays 20.f3 but never takes the hanging Black Nd4, perhaps hoping the knight would retreat with the idea of opening the b1-h7 diagonal. The obvious pawn-captures-knight would clog the diagonal and force the light-squared bishop to a less inviting square. It hints that White is unable to place a different piece to support the queen for checkmate on h7 or g7.
After 21...Bf7! the White queen is all but trapped, so White gives up a rook for the g-pawn to create a flight square to save his queen. Maintaining her safety limits some of the tactical devices available for White in the battle. She is unspectacular this day.
The en prise Black Nd4 does finally retreat five moves later with tempo on the White queen. Then Black is able to finally recapture the White knight on the queenside for a permanent material advantage, as well as a positional advantage having a battery that controls the open c-file. Black has his pieces positioned well, leaving White no entry points or sound sacrifices. When the b1-h7 diagonal finally does open, it's Black who plays 29...Bf5 to seize it! At that point, White dare not even pick off the undefended isolani, an uncommon sight.
White has four pieces trained at the kingside with nowhere to go, as Black has the situation covered with increased mobility. Sure, GK could have continued down material (rook for two pawns), but Black's accurate positioning makes it clear the underdog understands the position and has avenues to simplify. Eventually, the Black rooks would barrel into the White camp. White is unable to position another piece to help his queen get through.
Black simply has the better game with easy play ahead. GK saw the writing on the wall and wisely chose not to embarrass himself by playing on.