Also a modern idea.
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  7... a7a6 The main move. 8. a2a4 