Correct answer: Kd11...N:g3 2.O-O-O# 1...Nd2 2.Q:e3# 1.Nf2?? (2.Nh3#/N:f1#) 1...N:g3 2.Q:g3# but 1...e:f2+! 1.Nf6?? zz 1...Nd2 2.Q:e3# but 1...N