1.Nf3 f6

With this defense, white cannot play Ne5 or Ng5. White has three critical moves here:

2.e3, opening diagonals for the queen and the white bishop,

2.Nc3 for an attack with the two knights,

2.Nd4 trying to directly reach for the black king.

White can also try 2.d4 and 2.e4.

2.Na3 should not be a problem for black with 2...b5 (3.e3 e6).

If 2.Nh4 then 2...e6 or 2...d5 and black is fine.