Santasiere Variation

The Santasiere Variation arises after 1. d4 Nf6 2. c4 g6 3. Nf3 Bg7 4. b4. White forgoes the usual Nc3 or g3 and gains queenside space at once, but the advanced b-pawn is loosely supported. Engines therefore rate 4...a5, which challenges the pawn immediately, among the best replies, although 4...O-O and 4...d6 are the most common in practice. The line is rarely seen. Engines judge the position roughly balanced, and Black scores slightly better in online games.