1. d2d4  1... g8f6  2. c2c4  2... e7e6  3. b1c3  3... f8b4  4. e2e3  4... e8g8  5. f1d3  5... d7d5  6. c4d5  6... e6d5  7. a2a3  7... b4d6  8. d1c2 Both players are entering one of the most complex structures, a Carlsbad with a white dark-squared bishop behind the pawn chain. 8... a7a6 