1.Nh3 f6 2.Nc3 Nh6

A critical line starts with 3.Nd5 e6 4.c3 Ng4 5.f3 (5.f4) Bc5.

Another critical line is 3.g4 c6 then white can choose 4.e4, 4.e3 or 4.Nd4.

Other possible lines:

3.h3 Ng4 4.hxg4 c6,

3.Ne5 fxe5,

3.e3 Ng4 4.f4 c6 5.Nd5 cxd5 6.Bb5 Nc6 7.Ng5.