Exploiting the fresh protected square. Meanwhile, Black still can't develop his knight or queen's rook.
This helps Black gain space and bring his king closer, although White had no prospects.
4...f6 5.Bf4 Kf7 6.f3 g5 7.Rxd8 Rxd8 8.Be3 h6 9.Re1 f5 10.f4 Bf6 11.g3 a5 12.Nc1 a4 13.a3 Bc4!