zydeco: This game, Larsen's third loss in a row, effectively ended his chance of challenging Spassky for first place in this tournament.
On move 10, Larsen comments: "Typical of Spassky's opening play with black. A modest but very solid position. Let White try to find something!"
Actually, in Spassky's notes, he says that he was very concerned during the opening. White had a real advantage by move 10. Spassky planned 11....c5 but rejected it because of 12.e5 Nd5 13.Nxd5 exd5 14.Bxg6 hxg6 15.Qb3 cxd4 16.Bxd4 Nc5 17.Bxc5 Bxc5 18.Rad1. If you watch The Master Game (Spassky's game with Timman), he does something very similar: calculates a long line, doesn't like something about it and then settles for a 'half-move,' in this case 11.....c6, preserving some elasticity in the position even at the cost of essentially losing a tempo.
Both Larsen and Spassky feel that white played too slowly from around move 12 to 20. Larsen thinks he shouldn't have played 13.Re1 - and the rook could have supported the f-pawn from f1. Spassky decides to take the initiative on move 20.
28.d5 was "a serious miscalculation." Both players give the line 28.Nxg6 fxg6 29.d5 Rb3 with a probable draw.
32.Nd4 Bb3 could have preserved a draw, but Larsen missed 33....e5!
Larsen suggests 34.f4 Kd6 35.Be4 exf4 36.gxf4 Bb3 37.Rg3 but, "shocked, and with only three minutes left, I played two weak moves."
Spassky suggests instead 34.Rxe5+ Kd6 35.f4 Rc3 36.Be4.
Spassky wins the endgame very smoothly.