Black no longer has the possibility of …h7-h6, to drive this knight away. Now, White wants to follow up with ♕d1-g4-h4.
The somewhat awkward 13…♘e5 was better, preventing White’s plan, though White is still better after the persistent 14.f4 ♘5c6 15.♕g4.
Planning to follow up with ♗c1-h6, but other moves were equally good here.
12…♘fxd5 prevents the pin by ♗c1-g5, but allows 13.a3, and 12…♗xd5 13.♗g5 boils down to the same thing.
‘Black’s position resembles a prisoner tied by his legs and arms’ – Krogius.
13…♗e7 14.♗xf6 gxf6 15.♘xd5 ♗xd5 16.♗xd5 exd5 17.♘d4 ♔f8 18.♘f5 h5 19.♖xd5 ♕xd5 20.♕xe7+ ♔g8 21.♕xf6 1-0
14…♗xe4 can be answered with 15.♘d2 as well, or with the simpler 15.♗e2. After the suggested continuation: