There are 5 visualization pattern memory banks which you must acquire.
The one you are referring to, the middle game, is called middle game visualization patternmemory bank.
There are 4 other visualization pattern memory banks:
1. Tactical visualization pattern memory bank
2. Mating net visualization pattern memory bank
3. Opening visualization pattern memory bank
4. Endgame visualization pattern memory bank
You will have to acquire the 4 above memory banks before you can acquire the middle game visualization pattern memory bank.
The middle game memory bank has to do with knowing 6 characteristic pawn structures that result from every opening. Being familiar with the plans of attack in your selected opening repertoire based upon the defensive system selected by your opponent. And the indicated pawn break(s) for the particular plan of attack selected. Of course by then you will already know that the line between the opening and the middle game is usually a pawn break. The pawn break is the first move in the plan of attack selected for the middle game
[Couldn't find better forum]
When I'm around 15-20 move i don't know how to play, especially in closed position. If there's no point to attack or go in, my brain turns off.When analyzing my games with chess program i can't believe i couldn't see good moves in game....
How to improve my middlegame skill level?