1.Bg2? Kb5 2.Qb1# 1...c3 2.Qa4# 1...Kc3!

1.Qf3! Kb5/c3 2.Qb7#

b) 1.Qd6+? Kc3 2.Qd2# 1...Kb5!

1.Qd5! threat 2.Qa5#,Qxc4# 1...Kc3 2.Qd2#  1...b2 2.Qxc4#

c) 1.Qd7! c3 2.Ra6#

d) 1.Qd7? c3!

1.Qd8+! Kb7 2.Bg2#

The #2 homebase quadruplet represents a first for the directmate genre, even beyond miniatures. Each white piece of the three possible gives checkmate. The difficulty of the changing queen key decreases from part to part of the quadruplet.

Keywords: homebase (w), changed mates, flight taking keys (Q), checking key (Q)

Animation on PDB: https://pdb.dieschwalbe.de/P1408381