The Lacny or Lacny cycle is a chess problem theme named after Ľudovít Lačný , the first person to demonstrate the idea in 1949.
8-536: It is an example of lines of play being cyclically related: in one phase of play , the Black defences a, b and c are answered by the White mates A, B and C respectively; in another phase, those same defences a, b and c are answered by the White mates B, C and A respectively. The theme can be understood by reference to the problem to the right: this is the first problem to demonstrate the idea, by Lacny himself (first prize at
16-406: A phase). Each phase may contain a number of variations (lines arising from alternatives after the initial move of a phase; in a two-mover, for example, variations in the post-key play begin on Black's first move), but variations do not constitute distinct phases in themselves. In many problems, interest is created from the way in which the play in different phases relate to one another. Sometimes
24-399: The post-key play or actual play ; that is, the play after the key (the first move which leads to the problem's stipulation ("mate in two" or similar) being fulfilled). Other phases, which may or may not be present, are: A problem with n phases is called an n-phase problem . So a problem with set play and three tries, for example, is a five-phase problem (since the actual solution is also
32-429: The "simple" Lacny, and there are relatively few examples. In the related threat Lacny , short-cut Lacny or Dombro-Lacny , in one phase A is threatened, and defence b leads to mate B while defence c leads to mate C; in another phase B is threatened and defence b leads to mate C while defence c leads to mate A. Once, problems following this scheme were also called Lacnys, but now a distinction tends to be drawn between
40-495: The Przepiorka Memorial, 1949); it has been much-reproduced. The set play is: The key to the solution is 1.Nd2 (threatening 2.Nf1#), after which the mates are changed thus: As well as in set play (as in this example) the theme can be shown in tries , more than one solution or twins . The scheme can be expanded to include more defences; in a fivefold Lacny, for example, the defences a, b, c, d and e are met with
48-401: The mates A, B, C, D and E respectively in one phase and B, C, D, E and A respectively in another. The cycle can also be extended over three phases to make a complete Lacny cycle ; here, the defences a, b and c are answered by the mates A, B and C respectively in one phase; by B, C and A respectively in another; and by C, A and B respectively in a third. This is considerably harder to achieve than
56-502: The play in different phases has similar or contrasting motivation; sometimes the actual moves in different phases may change or transfer from one phase to another. Several basic ideas involving the relationship between different phases have been revisited again and again by composers and have acquired names; for example, in the Zagoruiko , at least two black defences are answered by different white continuations in at least three phases; in
64-592: The two (Peter Gvozdjak in Cyclone suggests this scheme should be called the Shedey cycle after its originator, Sergei Shedey ). There are a number of other themes featuring cyclic play in different phases, including the Kiss and Djurasevic cycles. Phase of play Phases of play are parts of a chess problem which happen, as it were, concurrently rather than consecutively. Each problem has at least one phase:
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