8...Nd7 should have been played.

White is virtually winning already.

Very nice! White won 10 moves later.

Right again! Not only because of the now half-open f-file, but also to be able to challenge White's centralized knight with ...Nf7.

With a favorable position for Black.

Stopping White's a4-a5 once and for all (though at the moment . . . b6-b5 seems a suitable response), not minding the b5 -square and the now backward b6-pawn. Black has a clear follow-up in mind though.

A fine post for the knight, from where it aims at the blocked a4-pawn and also supports the central advance of the e-pawn. After some adventures, the game ended in a draw.

Concrete chess. What counts is - as always- what will remain on the board after this surprising exchange. After White's next it becomes clear that Black's weak pawn on b7 will be increasingly hard to defend.