notyetagm: What a beautiful combination by Karpov, 32 ♖h8+! ♔xh8 33 ♕h1+ ♔g8 34 ♗xf6. In this particular position, 34 ♗xf6 is an amazingly powerful move, affecting <e7, f7, g7, and h7>.
First off, 34 ♗xf6 removes the f6-knight defender of the <h7>-square, creating the threat of the standard mating sequence ♕h7+ ♔f8 ♕h8#.
Secondly, 34 ♗xf6 places the White dark-squared bishop on the a1-h8 diagonal, pinning the Black <g7>-pawn to this line. This pin prevents Black from meeting the mating threat by blocking the b1-h7 diagonal with his g-pawn (34 ... g6 35 ♕h8#). But the resulting position is hopeless hopeless and so Black resigns. He could have resigned after 34 ♗xf6 but probably played on because he was in time pressure.
Thirdly, the White bishop on f6 blockades the <f7>-pawn, so that Black cannot make luft for his king by playing 34 ... f7-f6. Since the support for the White queen arriving on h7 is provided by the f5-bishop and not by a pawn on g6 or a knight on g5 (both of which also cover f7), vacating the f7-square would allow the Black king to escape the backrank mate if not for the fact that the pawn on this square was blockaded by 34 ♗xf6.
And finally, 34 ♗xf6 puts the bishop on f6 where it controls the critical <e7>-square, the flight square that the Black king needs to escape his first rank from the impending h-file invasion. <So the e7-square is not only self-blocked by the Black rook residing on this square, but the White f6-bishop also covers this important square.> If Black captures the bisop, then the self-blocking rook results in mate. If Black moves the rook, then the f6-bishop covers e7 and the result is again mate. <This double coverage of e7 is what Black (Morovic) missed.>
<To avoid mate, Black needs to both move the rook off of e7 AND capture the f6-bishop.> Since he has only one move for both, he was to do one with tempo (check). So Black sacrifices his queen so that he can move the rook off of e7 with tempo (34 ... ♕xg3+ 35 fxg3 ♖e2+) and then take the bishop (36 ... gxf6) to avoid being mated.