12 c4 Nc3 13 13 Qc1 QxQ 14 RxQ NxB 15 KxN Nc6 16 Be3 Be7 White opens the center with :17 d4 exd 18 Nxe NxN 19 BxN f7 20 Ra1 b6 21 Bf3 0-0 22 Rgb1 Rf b8 White is still down 2 pawns but very active
When down in material, one should do everything possible to avoid trading down; that goes doubly or trebly so with the Qs. Once the Qs come off the board, White's chance of a mating attack plummet. it's the last thing he wants to do unless it leads to an irrefutable attack.
Instead of 16. ... Be7, Black should play 16. ... c5, putting a hammerlock on the d4 square. Yes, it means his d pawn is backwards but Black wants to prevent White from opening the center currently. White cannot undermine the pawn chain since he cannot play b4. Since White has no e pawn to support d4, he can't open the center [yet; there's still the f pawn]. However, Black can at the right time with f5 and then e4 if he so chooses.
Ordinarily, White would counter by placing his N on d5 to exploit the hole [ie Ne4, then Nc3, then Nd5]. However, before he can pull this off, Black will play Nc6 then Nb4 so if White plays Nd5, Black will trade Ns and also leave White with doubled isolated pawns on the d file. White has no easy way of dislodging this N without wasting a lot of moves during which time Black can simply play Be6 which also defends the d5 square.
The Nb4 also threatens the weak d pawn which can be double attacked with Bf5.
White must counterattack quickly or get steamrollered in the endgame. Probably start with f4 to attack the central pawn mass. Black will support the pawn chain with f6. After the exchange, there will be an open f file which White will attempt to support since his Rooks are connected and Black's aren't.
Black advantages:
- Material: 3 pawns up
- 2 Bishops + N vs 1 Bishop + 2 Ns
- No mating threat by White
- Passed pawn
- K needn't castle now that the Qs are gone
- Pawn control of the center
- Ability to push central pawns at the right time
White advantages:
- Connected Rooks [for now]
- Control of the only semi-open file
- Better development
Here's how I see the game being played out if White plays c4:
10. ... Qxa2
11. Ra1 Qb1
12. c4 Nc3
13. Qc1 Qxc1
14. Rxc1 Nxe2
15. Kxe2 c5
16. Ne4 Nc6
17. Nc3 Nb4
18. Nd2 Be6
19. Rf1 Be7
20. Nde4 Bxg5
21. Nxg5 Ke7
22. f4 f6
23. Ne4
And a little trap I just discovered:
23. ... a6
24. Na4 b5
25. Nc3 ...
Not cxb5 axb5 where Black gets to keep his pawns connected and advance one more square. But there's a tactic in chess involving destroying the base of the pawn chain which makes vulnerable everything connected to it:
25. ... Nxd3!
26. Kxd3 Bxc4+
27. Kd2 Bxf1
28. Rxf1
Granted, White probably shouldn't fall for this tactical jab but one never knows.
Conclusion: White is not without resources but is considerably worse. With correct play on both sides, Black will win.