Block task

The block task ( English block ) is a task with an initial position in which White has an answer to any black move. There are several forms of blocks (mainly in the two-way ):
a) incomplete ( English incomplete block ) - the mat is ready for any move except one (incomplete zugzwang for black); at the same time, White’s opening move prepares an answer to this move;
b) with a wait-and-see 1st move (full zugzwang) ( eng. waiter ) - all prepared mats remain unchanged;
c) with the addition of the game - new options are added, in addition to those available in the initial position;
d) with the change of mats for some or all moves of blacks ( English mutate ) - the most common form, see examples No. 1, No. 2;
e) with the transition from zugzwang to threat in the decision ( eng. block - threat ) - cases d) and e) are often associated with tasks on the topic of changing the game;
f) with continued play (continued tasks) - initially the task is performed in the starting position, then after the first move of white in the solution of the first problem a new position appears with the same task and so on; in the case when in a new position he decides to return to the initial position of the previous task, they talk about “perpetual motion” (“perpetuum mobile”) or about the “pendulum type” block task (“pendulum”), see example No. 2;
g) pseudo-two-entry, pseudo-three-entry, etc. ( English pseudo-twomover, pseudo-threemover etc. ) - in the initial position without an introductory move, the task is completed in 2 moves (3 or more), however, after entering, more moves are required to solve , see example No. 3.