1.Nf3 f6 2.e4 d5

White has many possibilities:

3.Nc3,

3.d4 Nh6 (3...Bg4 4.exd5 e6) 4.Bg5 (4.Bh6) Bg4 5.exd5 g6,

3.e5,

3.Ng5,

3.Na3.