1.Nf3 f6 2.Nc3 Nh6 3.g4 c6

White can play:

4.d4,

4.e4,

4.e3,

4.Ng5 Nxg4 5.Bh3 e6 6.d4 g6 7.Bf4 d6 8.Qd3 Bh6 (or 8...b5).