1.Nf3 f6 2.e3

Black has to be careful here as there are many losing moves. For instance 2...Nh6 3.Ne5 fxe5 4.Qh5 g6 5.Qd5 followed by 6.Qxd7 or 6.Qxf7.

A good move is 2...e6. A tricky move is 2...d5.

If black plays 2...c6 then 3.Ne5 fxe5 4.Qh5+ g6 5.Qe5 (maybe 5.Qg5 Nf6 is even stronger) 5...e6 6.Qc7 Qxc7 and white is winning.

If 2...d6 then 3.Nc3 (or 3.Bc4 e6) then black has a difficult game:

3...Nh6 4.Nd5 e5 5.Bb5 and white is winning,

3...c6 4.Ng5 fxg5 5.Nd5 cxd5 6.Qh5+ g6 7.Qb5+ Nc6 8.Qb6. Now:

8...Kf7 9.Bc4+ d5 10.Qc7 Qxc7 11.Bb5 and white is two pawns up,

8...axb6 9.Bb5+ Kf7 10.Be8+ Ke6 11.f4 Qxe8 (if 11...Qa5 white is still winning) 12.f5 Kd7 13.Rf1 Rxa2 14.b3 and white is winnning,

8... Qxb6 9.Bb5+ Kf7 10.Be8+ Ke6 11.e4 Bh6 12.f4 b5 14.d4 Bb7 15.d5+ and white wins.