1. Main line 1. d4 Nf6 2. Nf3 g6 3. Bf4 2. Main line, 4. e3 1. d4 Nf6 2. Nf3 g6 3. Bf4 Bg7 4. e3 3. Main line, 4... d6 1. d4 Nf6 2. Nf3 g6 3. Bf4 Bg7 4. e3 d6 Next