An excellent measure of restriction, which takes the e4-square away from several black pieces, and soon d5 as well.

1...Nf5 2.Qc3 Bb7 3.e4 , keeping the advantage.

Fixing a target on a7. We can also notice that the bishop on a8 has turned into a very passive piece.

This leads to new weaknesses, but Black was short of constructive ideas.

Now White manages to swap the enemy's active queen. Preferable was 6...Nxf5 7.Qc3 with a clear, though not decisive advantage – Kasparov.

White later realized his extra pawn.

Restricting the enemy bishop and parrying the threat of 3 b5.

In contrast, 2...axb4? 3.axb4 is illogical since it opens the a-file for the white rooks.

The b2-bishop is no longer impressive, while the c4-pawn has turned into a weakness, something that Black soon exploits.

Followed by ...Rad8, leads to a clear black advantage – Keres.