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2…g6: hold d4 before opening up
Against 2…g6, you always take on f6. Two continuations cost you dearly: 4…d5 5.cxd5 (18 games, 25%, when 5.Nc3 scores 64% over 18 games) and above all 4…f5 (27 games, 26%).
Recall: against 3…Bf5, which black pawn are you aiming at?