Mate in 3
A problem whose idea has been shown a number of times but never in a better construction.
1.Qe2 threat 2.Qf2+ Sf3 3.Qxf3. 1...c4 2.Qe4+ A dxe4 3.Rf4 B;
1...d4 2.Rf4+ B exf4 3.Sxd4 C;
1...e4 2.Sd4+ C cxd4 3.Qxe4 A;
2...Ke5 3.Qxh2; 1...Rxg4 2.hxg4+ Sxg4 3.Qf3.
A crystal clear AB-BC-CA cycle of continuations and mates following moves from the third-pin arrangement of black pawns. A strong player as well as a top class composer, Alex Casa (1932-2005) represented Monaco many times in the Chess Olympics.