This problem by the Spanish composer and player Valentin Marin y Llovet (first published in 1910) is a beautiful example of early-20th- century ingenuity. It is White to play and mate in four. Black's king is surrounded, yet White is hard-pushed to concoct a check without losing his grip. The White queen is free to roam, but with g2 defended by the knight on e1, it is not clear where she should be heading. After 1.Qe8, Black plays 1...Nf7 2.Qxf7 g6 3.Qxh7 Nf3+ and White runs out of time.

The answer contains some beautiful variations: 1.Qd5! and now: 1...Ng6 2.Ne6+ Kh5 3.Nxg7+ Bxg7 4.Qxf5 mate; or 1...Nf7 2.Qh1!! Ne5 3.Rg3+! hxg3 (or 3...Ng4 4.N2h3 mate) 4.h4 mate; or 1...b5 2.Rc3!! h3 (or 2...dxc3 3.Ne4+ Kg4 4.h3 mate) 3.Qxf5!!+ Kxf5 4.Rxc5 mate. 1...c4 and 1...d3 are similarly met by 2.Rb3!! and 2.Rxd3! The surprising point is that after 1.Qd5! White has no threat of mate in three. Black is in total zugzwang.