The middlegame transposed to the endgame.
Enjoy. I have also analyzed this game.
The rules of the middlegame:
If you are ahead in material, exchange pieces and simplify to a winning endgame.
If you are losing in material, avoid exchanging pieces.
If you are winning by pawns, exchange pawns, but not pieces.
If you are losing by pawns, exchange pieces, but not pawns.