5.c5 Bb3 6.Nb6 Nxb6 7.axb6 a5 White ends up with a bad pawn structure.

The c-pawn is gone, but the c4-square remains weak.

At first sight this passed pawn doesn't seem too powerful, but it will soon be.

Fighting against the blockade on c3. The game continued:

Black has a decisive advantage.

A strong exchange sacrifice that ruins the black pawn structure.

1...Qxc5? 2.Qxc5 dxc5 3.Bxe5 White regains the material with interest.

Just in time, before Black plays ...f7-f6.

8...Nd6 9.Nxd6 Qxd6 10.Rxa7 +/-

Preventing Rb1+ and preparing 12 Ra5 with an attack on the a7-pawn. The latter also enables a future c4-c5 with a huge advantage.