Chess Opening Theory/1. d4/1...g5/2. Bxg5

=2. Bxg5: Borg Gambit Accepted=

First Impressions
After accepting the Borg Gambit with Bxg5, White has gained a pawn as well as developed the queenside bishop. Obviously, this puts Black at a disadvantage, as White is now leading in development. Black has three main options here: Play the better move Bg7 and commit to a pseudo-Indian defense, c5 to try to destabilize the center and let the queen out, or try to kick the bishop out with f6.

2... Bg7
Bg7 prioritizes development over central control, and is considered better by masters and computers alike. This move aims to get quick development up in exchange for gambiting the g pawn. White can fight back by expanding in the center and developing their own pieces, leading to a rather quick race for who can develop their pieces the fastest. This gambit is usually considered not justified.

2... c5
The intent of c5 has two reasons. First, it is to destabilize White's center pawns and force them to respond lest they lose space by a center pawn being taken by a flank pawn. Secondly, it is to let the queen out, which can help destabilize the center or hunt the b2 pawn. This also develops a piece, getting a bit of advantage back for Black.

2... f6?
f6 attempts to kick away the bishop and expand in the center with an eventual e5, but this can be refuted with 3. e4!, saving the bishop for 1 turn and making some center space. If Black tries to take the bishop, the White queen can go to g5 for a quick checkmate. Overall, this line is considered inferior to Bg7 by masters and computers.

Other options
Black can also play Nf6 to develop the kingside knight, however after Bxf6, there are doubled pawns on the f file and there is a clear line of sight to the king which can be exploited since the kingside pawns are weak.

Theory table
1.d4 g5 2.Bxg5