1. g1f3  1... d7d5  2. g2g3  2... g8f6  3. f1g2  3... c7c6  4. c2c4  4... d5c4  5. e1g1  5... e7e6  6. a2a4 White follows a plan to regain the pawn on c4. It's also possible to sacrifice it. 6... b8d7 