The main move.
1. d2d4  1... d7d5  2. c2c4  2... e7e6  3. g2g3  3... g8f6  4. f1g2  4... f8e7  5. g1f3  5... e8g8  6. e1g1  6... d5c4 One of the oldest and most solid lines against the Catalan. 7. d1c2 