Modern Defense

B06

About this opening

Black fianchettoes before committing a single center pawn, which is the most flexible way to meet a king's pawn opening and also the most demanding to play well. The bishop will sit on g7 and stare at your center from a distance. d4 is the most played move here and it is right: take the whole center and make Black prove the idea. Nf3 and Bc4 are reasonable but modest. The practical point is that Black has no pawn in the center yet, so every move you spend building one is a move Black cannot easily challenge, and you should build quickly.

Plans

Play d4 and take the center Black is refusing to contest.
Add c4 for a broad center and more space.
Develop Nc3 and Be3, then consider castling long.
Meet the fianchetto by keeping the long diagonal blocked.

Where the pieces belong

Pawn: d4, the center you should build at once
Pawn: c4, widening the center
Knight: c3, holding d5 and e4
Bishop: e3, defending d4 against the fianchettoed bishop
Pawn: f4, gaining space before the attack

You take space, Black waits and strikes with c5 or e5. Keep the long diagonal blocked and your center defended, and the extra space becomes a lasting advantage.