comment: The system with c6-d5 in the Grunfeld Fianchetto has been played in thousands of games, even at the world championship level. It's one of Black's most solid options.
context: 1. g1f3  1... d7d5  2. g2g3  2... g7g6  3. d2d4  3... f8g7  4. c2c4  4... c7c6  5. f1g2  5... g8f6  6. e1g1 