Ulhumbrus: This game may be worth comparing with the famous game Lasker vs Tartakower, 1923
The move 6 h3 moves a pawn in the opening and this suggests that it is the cause of White's coming troubles.
It may be that 6...g6!! is a brilliant stratagem whose purpose is less obvious than an immediate attempt to take advantage of 6 h3.
The idea may be as follows.
The move 6 h3 loses a tempo for development and disturbs the king ide pawns.
These are the more obvious concessions which the move 6 h3 makes.
However a less obvious concession which the move 6 h3 makes is that it makes it more difficult for White to take advantage of 6...g6.
Thus the idea may be that instead of trying to take direct advantage of White's concession Black himself makes a concession of which it has become more difficult for White to take advantage of.
All the same, Lasker did employ the move h3 in the famous game Lasker vs Tartakower, 1923 and this suggests the question of whether Black can gain more than Tartakower did.
One difference between this game and the game Lasker vs Tartakower, 1923 is that Lasker played 6 Bf4 whereas Anand has prevented the move Bf4 by his move 5...Qc7.
Tartakower spent the tempo which Anand has spent on the move 5...Qc7 on playing the move ...Nc6 and so allowed Lasker to play Bf4.
This suggests that on 4...Nf6 5 Bf4 pre-empts the move 5...Qc7 and one justification for this move is that Black has delayed attacking the d pawn by 4...Nc6 and this suggests that White can afford to delay defending it by c3.
With 7...Bf5 Anand plays once again differently from Tartakower who advanced his f pawn by 8...f5.
10 Bxf5?! strengthens Black's centre and although the recapture 10...gxf5 disturbs Black's king side pawns Black has not committed himself to castling on the king side yet and may be able to do so all the same eg if he plays his other N to g6.
11 Nd3 withdraws the N from e5 whereas Lasker kept it there and waited for Tartakower to take it.
By now there are quite a number of differences between this game and the game Lasker vs Tartakower, 1923
12...Rg8 more or less declares that Black is going to castle on the queen side. Van Foreest decides to castle on the king side despite the opening of the g file. One justification for this choice is that White seems able to try to attack only on the queen side perhaps by c4 and castling on the queen side makes it more difficult to arrange this pawn advance.
17 b4 seems inconsistent. Having castled on the king side and so made the advance c4 less dangerous he advances the b pawn instead.
The computer analysis suggests that the move 21...f4! prepares or begind an attack on the g file, an attack which succeeds.
With 26...Nxg2 the attack on the g file has broken through. We can assume that Van Foreest expected to be able to defend his king despite the opening of the g file and this suggests that there is at least one thing or one detail which Van Foreest has not seen in time, for example, one of the consequences of the pawn advance 21...f4!