? 15.Nxd4 exd4 16.f4 gives White some tempo and space on attacking Black's Kingside
15. Bb2xd4
? White missed this, instead opting for the equal trade
15... exd4 16. h4 Be6g4 17. Qe2c4 Kg8h8 18. Nf3g5
? An unsound knee-jerk reaction move, looking to sac the exchange for a potential mating sequence on the King i.e. 18...Bxd1 19.Nf7+ Kg8 20. Nh6++ and we have the philidor's mate (18.h4-h5 instead was better)