1. e2e4  1... c7c5  2. g1f3  2... d7d6  3. c2c3  3... g8f6  4. f1d3 This is not the most popular of the Anti-Sicilians, but it still has close to 5,000 games in my database. White's idea is simple: the bishop goes back to c2 and then the d-pawn will be advanced one or two squares. The problem with this variation is that Black manages to develop the pieces without any problems, so it's not difficult to equalize.