|twinlark: This was a really nice game by Smerdon even if the Tal-like Knight sac on move 19 was unsound; the practical chances it offered must have looked overwhelming to Black.|
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Black declined with <19...f5>.
<19...fxe5 20.Ng5> threatens mate in 1 with <21.Qh7#>, mate in three starting with <21.Bh7+>, and to win the queen with <21.Nxe6> and <21.Nf7>.
<20...h6> staves off all except <21.Nxe6> which sets off a tactical melee that favours White. The best defence by Black seems to be <21...Bd7> when <22.Bxh6 Bh5 23.Bh7+> and it's on for young and old.
However, <20...h5> holds the game with advantage to Black, even with moves like <21.Qxe6+>, <21.Nxe6> and <21.Bh7+> available to White.
Black can't be blamed for avoiding these complications, especially as nothing disastrous happens if he declines it. He gets a perfectly nice game, and then gets over anxious by offering the queen exchange when almost everything other moves is perfectly ok.
Smerdon must have made him nervous!
It's all over in another 7 moves, with <34...Nf4?> being the losing move. Black resigned as he can't defend against the threat of <37.Rh4>.