Introduction

I will have 2 positions and try to show how much of a difference one move can make.
This post is inspired by a game I played badly and lost, I suspect that the complications from the opening was a bit beyond me and let to me having no good ideas, and the position got really bad, so now I want to learn about this variation.

This occurs after

1. d4 Nf6 2. Bg5 c5

c7-c5 has a rather clear idea, in fact two ideas.

1. Pressure against the center
2. The queen can come to b6 and putting more pressure on the center, but also on b2.

But in this position white had an idea with Bg5, he wants to take the knight on f6.

3. Bxf6

Here black has 2 responses I think exf6 is better since he is likely to castle on the king's flank, so opening the g-file might not be a brilliant idea, at least it will increase risk.

3.- exf6

However this means that black is accepting a not so good pawn structure, d5 could be isolated and the king-side pawn structure is a bit messed up, and he only has a moderate amount of pressure against b2, so perhaps this is not the best version, but there is a version of this that makes everything a lot more complicated.

2.- Ne4

This occurs after 2.- Ne4 3. Bf4 c5
This position is in fact what I played against and could not figure out, I think this position is a lot more complex.

The mainline is 4. f3 (this is a very common move in the trompowsky after the knight gets to e4).

In this position black has a zwischenzug 4.- Qa5+ white more or less has only one response to this 5.c3
then black has to move the knight back 5.- Nf6

White has a decision to make here.

6. Nd2 or 6. d5, I however played badly here, I think white should do fine with either of these moves
perhaps Nd2 is slightly better, but also a bit more complicated.