If white had looked a little harder he might have found <30.g5!>:

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Now after <30...hxg5 31.Kg2> black no longer has ...Nf4+ as a threat (31...Nf4+ 32.Rxf4). If he leaves the N where it is then it can now be safely taken whilst <31...Nd4 32.hxg5 Qd8 33.f6+> wins at least the exchange and probably the game.

He plays Kh8 twice and Kg7 twice. One of these is obvious, one is forced and one is a downright error (see my previous post).

I thought black was better with that power-house knight on d4, for example, on move 17, I thought that knight was the best minor piece.

But Stockfish said the game was even.

Ok, then when we get to move 28, I was surprised that white is viewed as up about a whole pawn - again, I thought that knight was very strong for black.

But Carlsen made a bad blunder in he maneuver to get the knight to f4. After white's 29th move, white is still up almost a pawn:

1) +0.96 (20 ply) 29...Rhg7 30.Bg2 Nd4 31.Qd3 Rc8 32.Bd5 Rd8 33.Qe3 Rdg8 34.Rf2 b5 35.cxb5 Nxb5 36.Be4 Nd4 37.Rfg2 Qd8 38.Bb7 Qf6 39.Rf2 Kh7 40.Bd5 Kh8 41.Be4

But then Carlsen makes what should be the losing move - Kg7?

I was surprised this is viewed as losing, and even more surprised at white's shot here - 30 g5!,as Goodevans said above. It looks like both the pawn and the knight can just take the impudent pawn, but both lose!!

Best line is:

1) +2.24 (23 ply) 30...Nxg5+ 31.Kg2 Kh8 32.hxg5 Rxg5 33.Kf2 Rhg7 34.Rh3 Rg4 35.Qe3 Rh4 36.Ke2 Rgg4 37.Rxh4 Rxh4 38.Rg1 h5 39.Kd1 Rg4 40.Kc2 Kg8 41.b4 Rxg1 42.Qxg1+ Kf8 43.Qe3 h4 44.Kc3

So lets look at the tactics, which shocked me. What about 30 hxg5? White can't even take back! But white plays 31 Kg2. And now black is in trouble.

The tactical point is the wonderful looking outpost on f4, defended by 2 pawns, cannot be used. 31 .. Nxf4?? loses to 32 Rxf4! Of course the g pawn can't recapture, this is why Kg7 loses. And if 32 exf4? 33 Rxg5ch wins the queen!

So what about (going through the sequence) 30 g5! hxg5 31 Kg7 Rxh4? 32 fxe6.

If black plays Qxe6 white wins with 33 Bd5! followed by taking on f7.

So 30 g5! hxg5 loses. What about 30 g5! Nxg5 ? Well then 31 Kg2 simply wins the knight, however it is black's best.