Try: 1.Rd1? (thr. 2.Rd3#) but 1…Bxc6! Key: 1.O-O-O! (thr. 2.Rxd3#) Bxc6 2.Rxd3+ Ke4 3.Re1+ Kxf4 4.g3# 1...Ke3 2. Rde1+ Kf2 3.Sxd3+ Kg3 4.Re3# 2...Kxf4 3.Sxd3+ Kg3 4.Re3# 1...d2+ 2.Rxd2+ Ke3 3.Sc4+ Kxf4 4.Bd6# 1...Ba6 2.Kd2 (thr. 3.Sf3#) Sg5 3.hxg5 any 4.Sf3#
Double castler.
