1. Main line 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 Choose a line 1. Main line 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 2. Main line, 4... Nf6 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 Nf6 3. Main line, 5. O-O 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 Nf6 5. O-O 4. Main line, 5. O-O 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 e6 5. O-O Close 1. Main line 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 2. Main line, 4... Nf6 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 Nf6 3. Main line, 5. O-O 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 Nf6 5. O-O 4. Main line, 5. O-O 1. Nf3 d5 2. g3 c5 3. Bg2 Nc6 4. d4 e6 5. O-O Next