Glossary of Chess Problems - P

P

Phase

Play after the key, after tries and set play each constitutes a phase of play. A problem with set play is said to have two phases (the set play being one phase, the post-key play being another); a problem with three tries would be a four phase problem (each try being one phase, with the post-key play the fourth). Play in different phases will sometimes relate to each other.

Pickaninny

A problem in which, at some point in the solution, a black pawn on its starting square makes each of its four possible moves (forward one square, forward two squares, capture to the left and capture to the right). If the same behaviour is exhibited by a white pawn, it is an albino. (The term, which derives from an archaic reference to small black children, has a potentially derogatory meaning in modern English.)

Plachutta

A sacrificed white piece can be taken by two similarly-moving black pieces--whichever piece makes the capture, it interferes with the other. Essentially a pair of Holzhausen interferences (or a Wurzburg-Plachutta interference) brought about by a white sacrifice on the critical square.

Post-key play

The play following the key, that is, the lines of play which fulfill the stipulation of the problem. This is opposed to set play and virtual play (both of which may also be important elements in the attractiveness of a problem).

Proof game

A type of problem in which the job of the solver is to construct a game of a given number of moves in which the final position is the one given by the composer. A kind of retrograde analysis.

Pure mate

A mating position in which the mated king and all vacant squares in its field are attacked only once, and squares in the king's field occupied by friendly units are not also attacked by the mating side (unless such a unit is necessarily pinned to the king to avoid it interposing to block the check).