1.Nf3 f6 2.Nd4 Nh6 3.e4

Black can play:

3...Ng4 4.f4 Ne3 5.dxe3 d6 (or 5...d5 and black is fine) 6.f5 h5 7.c3,

3...c6 4.Nf5 Nxf5 5.f4 d5 6.f5 e5 7.d4 g6 8. c3 h5 or 7...h5 8.c3 (or 8.Na3 Bxa3 9.b4 a5) g5 9.exd5 c5.