Rather restrained, but I wouldn't call the move weak, exactly. The light-square bishop is not seriously incommoded, as it is intended to act on the a2-g8 diagonal, or maybe the a4-e8 if the opportunity arises. Meanwhile, White stakes out a modest but solid claim on the centre, and frees his Q-bishop for action. A good move, if not necessarily the best.

I expected White wanted to settle the Bishop in the center with 6. Bd5. After c6 the Bishop is not safe against b5. The Bishop is not protected and can be immediately attacked by 5. ... Na5! 6. Nc3 Nxc4 8.dxc4 and White loses tempo.

d4 looks better. But there is nothing wrong with this move.

Instead of exchanging on e6, White might have considered 8.Bb3, putting the onus on Black to decide whether or not to exchange. It would seem black would be ill-advised to exchange then on b3 as the opening of the a-file would be welcome for White, and Black's remaining bishop would be the so-called "bad" one: hampered by its own pawns. With the text, White does exchange a quite good "bad" bishop for Black's "good" bishop, but the strengthening of Black's centre, and opening the f-file is by no means inconvenient for the second player!

There is no white pawn ahead. 11. dxe5? is not recommendable. As Capablanca said, always beat with the king pawn in front of the uncastled King if you can. 11. dxe5? Nxe5! 12. O-O because 12. .... Nxf3 13. gxf3 destroys the pawn castle. So, the e-pawns have to take action, but 10. ... Bxf6 11. exd5 exd5 12. dxe5 Nxe5 13. O-O Nxf3 14. Qxf3 c6 15. Qd3 gives clear advantage to Black and control over the e-file.

In playing this move, Black would have had to calculate the likely consequences of 10.Bxf6 in response. It's more complicated than it looks! Here's a sample: 10.Bxf6 Bxf6 11.dxe5!? Nxe5!? 12.exd5 ... Is this winning a pawn? 12...exd5!? 13.Nxd5? Nxf3ch 14.Qxf3?? Bxb2 etc. But 13.Nxe5 Bxe5 14.Qxd5ch Qxd5 15.Nxd5 Bxb2 16.Rb1 Be5 17.Rxb7 leaves White a pawn ahead. Plenty of room for investigation, methinks! *** (in response to jprante 's comments) I think the jury is still out on 10.Bxf6 Bxf6 11.dxe5 (my !? notation indicated that I'm not sure about it myself!). After 11...Nxe5 (Black ought to consider other moves too, but this might well be best) 12.0-0?! Nxf3ch 13.gxf3 Bxc3 14.bxc3 leaves White's entire pawn structure in disarray. But 13.Qxf3 looks playable (13...Bxc3 14.Qxc3 dxe4 when Black's extra pawn resides doubled and isolated on the e-file). But I still reckon (until persuaded otherwise!) that 12.exd5 is playable. Better than Black's immediate recapture on d5 (as I suggested earlier) is 12...Nxf3ch 13.Qxf3 Bxc3 14.Qxc3 exd5 after which Black might have a whisker of an edge, but a draw seems likely, for mine.*** Bear in mind, my comment was intended to indicate that Black's 9...d4 was no trivial decision, not that it was a good or a bad move. The lines I gave were obviously not comprehensive, and there are still lines we haven't looked at...

The e5-pawn isn't too bad a weakness (if indeed it is one!). But White doesn't have much to console him for his shattered Q-wing.

After 13. ... Na5 and 14. ... Rf5 White can not hold the pawn e5, because Raf8 will begin to stress the knight f3. Black's attack is introduced by c5 followed by Qc7, which brings zugzwang to White, and Black will take Nf3 sooner or later.

I was expecting Black to play 13.Rf5 looking to place pressure on the e5-pawn before white can make arrangements to bring forward the f-pawn in support, then to double rooks and maybe bring his Q to h5 or g7. White dare not play g4, and thus weaken his K-wing.

The reason for Rf4 was 15. g3 Rf7 (weakens Knight) or 15. Qd2 Raef8 (the Queen would have been better placed with Qe2 otherwise).

Begins a very fine combination...

After 24. Kg2 Rxf3 White can successfully defend with 25. Qxd4 Qxh3 26. Kg1 Rg3 27. fxg3 Qxg3 28. Kh1 Qh3 29. Kg1 Nf3 30. Kf2 Nxd4 31. Rxd4 with a long end game, black queen against two white rooks.

White's last two moves constitute a neat finesse, in comparison with the prosaic 22...Nxf3ch 23.Kf1 Nxe1 24.Kxe1 Qh4 when Black should win the ending with his two-pawn surplus. However, Black seems to underestimate just how strong his attack is... At first I thought 24...Rf3 won more quickly, but jprante demonstrated that after 25.Qxd4 (a move I had glanced at but underestimated) White at least survives into the endgame with 2R vs Q, though I felt the 4-pawn surplus ought to be decisive. Having taken the time to have a closer look, I find that indeed 24...Nxf3 is more immediately decisive (and thus stronger) than 24...Rxf3. But it turns out that Black has a third alternative that wins even more quickly: 24...Qg5! (as played in fact) and if 25.Kh1, then 25...Qf5! 26.Rb3 Rf4! threatening (inter alia) ...Rh4 and ...Qh1 mate.