1. d4 Nf6 2. c4 c5 OK, so it is an offer of a free pawn, the problem is that if taken it weakens whites pawn centre and is usually returned with interest anyway. My QA tournament round one game I tried dxc5 and died pretty quickly trying to hold the pawn
3. d5 Seems to be the sensible way to go. Other options include Nf3 preparing to recapture with the knight which would eventually be kicked ( b3 looks like a nice post though ) , Bg5 where black looks strong after e6, Nc3 preparing recapture with the queen which will be harrassed, or Be3 which may not be as bad as it looks after a kingside fianchetto
b5 Attacking the base of whites pawn centre. Black will also probably try to attack the head at some stage with e6 also. This is the second gambit taking the game from the Benoni into the Benko gambit.
4. cxb5 Again here the free pawn will be given back, Black hopes that he will get a development lead open queenside while white hopes that he can use the centre and kingside space. Other options here are b3 or e3 preparing to recapture, but b4 causes problems by making Nc3 impossible, meaning that e4 is not an option. Trying to take b4 apart by playing a3 fails to Qa5 pinning the pawn to the rook until the bishop and knight develop, and also lines up a a discovered check on the king
a6 The third gambit pawn offer. Black hopes for bxa6 Bxa6 with blaxks queen to come to b6. Black would then have a rook and queen lined up with whites remaining queenside pawns, and a bishop and queen eying whites undeveloped kingside
5. b6 White offers a pawn back. Leaving it on b5 would let the a-file be opened, this way it stays closed, meaning that black will have to spend tempos to activate his queen rook.
Qxb6 6. Nc3 This is an outpost for the knight, no pawn can kick him off.
Bb7 7. e4 Trying to hold the centre to make blacks queenside development worthless
d6 This move seems to be against what black was trying to achieve. If black now wants to get rid of d5 he will have to support e6 with f7. Losing f7 will open a crack into his kingside. playing e6 here instead would at least be supported by d7, so white would not be eager to trade
8. Nf3 d5 is attacked twice and defended thrice, so has a free choice of move ( e6 is not a worry since e6xd5 e4xd5 leaves the queenside blocked and white still in control of the centre. The main trap here is that whites dark square bishop is the sole defender of the b-pawn, so must remain on c1 for a while
h6 Makes no sense. g6 and a fianchetto would have allowed blacks king rook and king bishop to enhance the queenside pressure
9. Bc4 Preparing to castle. Be2 is defensive, but there is nothing to defend as black has no kingside pressure. Bd3 would block the queens protection of d5 so black could play e6 and white loses a tempo
Nbd7 The only move the queens knight had, but it still has no moves on d7 ( Nd7-e5 is poison )
10. O-O White doesn't need to castle at this point but there are no better uses for the tempo
O-O-O Black was probably safer just staying in the centre. Black has big problems now. His king has no pawn protection, his dark bishop can't move and locks in his king rook his d7 knight is essentially immobile, and castling queenside took the queens rook out of action! Blacks queen is lonely on the b-file.
11. Re1 Threatening e5 opening the centre when whites mobility advantages should tell
h5 Black has no plan, he started in an opening trying to dominate the queenside, now he has only one useful piece on the queenside and one useful piece on the kingside ( kings rook ) .
12. Rb1 Preparing eventual control of the b-file, lining up blacks queen, and protecting the b pawn so that whites dark-square bishop can participate.
Qb4 The lonely queen attacks the hanging bishop, but why? it can be easily protected, and the queen on b4 will be easily harrassed, and has few retreat options
13. Nd2 This knight isn't needed defensively as the one piece kingside attack will never work, so swing it over for a queenside attack
Ne5 Attacking the bishop twice, which is only defended once. Unfortunately white has a bigger counter-threat
14. a3 Attacking the queen which has very little mobility
Qa5 Qb6 also turns out bad after b4
15. Bf1 b4 makes white uncoordinated after cxb4 axb4 Qc7 ( attacking bishop and knight ) Qb3. Nb3 Qc7 leaves the b-pawn blocked. Bf1 keeps the useful bishop
g6 trying to get the bishop into play
16. f4 White would like to play Nc4 forcing the queen back to c7 where she is almost immobile. White can't do this while black has a knight on e5. f4 get srid of the knight. It either has to go further away from the queenside, or will go to d7 where it takes more squares ( mobility ) away from blacks queen and king
Neg4 17. h3 Forcing the knight completely out of play
Nh6 18. b4 White could have played e5 here, forcing the other knight to d7, but I decided it would probably want to be there to defend the king, so no point forcing it to a 'good' square
Qb6 Slightly better was Qb7
19. Nc4 Coming into the attack with tempo, and threatening a5 and b6
Qc7 20. b5 threatening b6 which robs the queen of more room
Bg7 connects the rooks. Unfortunately they are still useless
21. bxa6 So many tactics available. This one immediately wins at least a bishop
Bxa6 Ba8 drags things out longer
22. Nb6+ Kb7 23. Bxa6+ Winning the bishop. The king cannot take it, as follows
Kxa6 24. Qa4+ Kb7 25. Na8+ 1-0