Ladislav Prokes composed this windmill study together with one of the greatest Czech players, Oldrich Duras.
1.f4+
Kg4
2.Qg3+
Kf5
White uses the mill to get rid of the pawn on e5.
3.Qg5+
Ke4
4.Qxe5+
Kf3
5.Qe3+
Kg4
6.Qg3+
Kf5
Without the black pawn on e5, white has time for a quiet move, threatening mate.
7.f3!
[However, both Ivo Novak and Noam Elkies discovered a dual solution, allowing the white queen to swing in two directions: 7.Qxd3+
Kf6
8.Qc3+
Kf5
9.Qe5+
Kg4
10.Qg5+
Kf3
11.Qg2+
Kxf4
12.Qg3+
Ke4
13.Qe3+
Kxd5
(13...Kf5
14.Qf3++-
) 14.Qb3++-
]
7...Qxd5
[7...Qf6
8.Qg4#
]
8.Qg5+
Ke6
9.Qxg6#
1-0