p1: In Sicilian Rossolimo land, Carlsen retreated LSB Bd3 instead of Bf1, with the idea of c3 and dropping back the bishop Bc2 pointing towards Topalov's kingside, and claiming the center with d4. After 6...b5 7.c4, Topalov played 7...g5 novelty. In these days, super GMs live to ignore opening principles. After 3 moves (8.Nxg5 Ne5 9.Be2 Bxc4 10.Na3 Rg8 11.Nxc4) later Carlsen answered the craziness with craziness, sacrificed a knight for two pawns. Main idea here is to checkmate Topalov's king in the middle by trying to open up the center for the rooks (center push also misplaces black's knight against a kingside attack), despite black has a resource: to sacrifice king's rook for white's remaining knight.
In p2, he could reach the full compensation with 17.Nxf8. However he played 17.e4? and overlooked Topalov's threat neutralising manuver 17...Qc6 (#1 Qxg2) 18.f3 (defending against checkmate) ...Qg6 (#1 and also N@h7 is hanging) So, queen trade is forced.
If 17.Nxf8, black needs to be careful and precise. Black can not recapture the knight right away. Now, you need to solve the puzzle to see the hidden variation and continue from there
At the end of ...Qh3 variation, if black moves R@g7 away (e.g. ...Rg8 to recapture the knight) and gives white's N@f8 h7 square (Nh7); ...f6 push still keeps the Knight trapped, but it costs the pawn because of Nxf6. Notice Bh6 doesn't give enough protection to the Knight. Bh6 Rg8 Nh7 Rh8! Nf6+ exf6 Bg7 Rh5 Bxf6. Conclusion: black is gonna recapture the knight at the cost of 1 pawn anyway (3 pawns vs. a piece imbalance). Never rush! Make some other useful moves! e.g. ...Rc8 or ...Nc4 in this case.
Another game with ...g5 is played between Aronian and Caruana.
They built up an amazing tension with:
16.Bxd6 Nxd6 17.Re1 a4 18.Nd2
...e5 19.e4 f5 20.f3
Spearmen are charging to eachother. How to resolve that high tension? How about bringing more wood to the fire? Black to move.
Firstly black's king is the weaker one. If the center randomly opens up, white will be on the attack.
White is threatening to capture dxe5. If it were white to move:
Is Aronian threatening to capture f-pawn also? Would that give life to Caruana's bishop? Well if exf5, black's e-pawn is hanging.
i) ...exd4 g4! will freeze black's bishop
ii) black recaptures f-pawn ...Bxf5 dxe5! or ...Nxf5 Qxe5!
But it is Caruana to move. Maybe there is a counter threat to ignore all of Aronian's threats. Black's candidate moves which come first to mind are pawn captures: dxe, fxe, exd. Caruana went for 20...dxe4.
There were also tension keeping candidates. ...Qf6 can be met by exd5 exd4 Nc4 where white's c and d pawn duo is very strong. The best move was ...Re8! defending dxe5 and in case of exd5, ...exd4 is challanging the e-file results in liquidation of white's attack. Now I'm gonna leave here a variation in ...Re8. Please visualise the pawn capture lines and ...Re8 line and feel the tension that top grandmasters feel. Enjoy the rest of the tournament.
...Re8 Qf2 Ra5 exf5 Bxf5 Bxf5 Nxf5 dxf5 d4