1.Nh3 f6 2.e4 d5 3.Na3 b5 4.d4

The most played move here is 4...Nh6. Other possibilities are:

4...Bh3 5.f4 (or 5.Qg4) c5,

4...Bg4 5.f3 Bxh3 6.exd5 e6 7.d5 Bd6 8.Bd3 g6 9.f4 h5 10.h4,

4...g6 5.Bh6 Bg4 6.f3 Bxh3 7.c3 g6 8.h4 e6.