other lines seem to play in black's favour too, so 11... 0-0-0 makes perfect sense to me, it's a clever move designed to entice white to take the bishop. and well done white for spotting the danger, and castling quickly.
♡ 47 ( +1 | -1 ) In his monograph on the Centre Game...... L.M.Pickett (1976) gives this line, observing that 12.fxg4 "leads White into difficulty": 12 ...Bh4+ 13.Kd1 Rhe8 14.Qd3 Qxg4+ 15.Be2 Rxe2 16.Qxe2 Qxf4 17.Kc1 Nd4, which Paul Keres assessed as (+/-). It seems that 12...Rhe1 or 12...Bc5 are also likely to lead to a Black advantage. In view of the threatening stance Black can take up after 12.fxg4, it would appear best to be avoided - unless you want to exercise your defensive technique! Cheers, Ion
♡ 92 ( +1 | -1 ) Fair question ...... and indeed Pickett passes it by without comment. Looking at the position, though, it is a difficult move to go past. It looks logical, to cut off the bishop's action along the white sqaures in White's field.
11.Be2 Nd4 looks rather unpleasant, inducing the bishop to move again: 12.Bd3. Against any other bishop move, Black just develops normally with 12.0-0-0. An illustration of what a nuisance the g4-B can be is this horrible possibility: 11.Bc4!? 0-0-0 12.Bxf7?? Bc5! 13.Qxc5?? Qxd2+ 14.Kf1 Qd1+ 15.Rxd1 Rxd1#.
So, given the position at move 11, f2-f3 seems to be called for. After 11.f3 0-0-0 12.0-0-0 Black really does have to move the bishop. At liege in 1930 Frank Marshall tried to sac the thing by 12...Rhe8 against Sultan Khan, and got axed in 22 moves (13.fxg4 Bg5 14.Qf2 and already Marshall didn't have enough attack).
Having said all that, both sides have other options, especially Black at move 4 and White at move 6.
♡ 17 ( +1 | -1 ) "Ok, but then why did white play 11. f3 ?"
absolutely, but it is possible that white was unaware of the danger until black player 0-0-0, then he analysed and realised he wasted a move!