Original Retro & PG problems
Definitions: (click to show/hide)
The -N & #1 stipulation means: retract N moves and then the White (forward) mating move.
Defensive Retractor: In Defensive Retractors, White and Black retract (take back) a given number of moves (-n moves), in order to reach a position in which a forward stipulation (e.g. #1, s#1) is met. Given a choice, Black will retract those moves that avoid or delay White’s goal. Unless otherwise stated, Black may defend by mating White through a forward move, if such an opportunity exists after one of Black’s retractions.
The different kinds of Defensive Retractors only differ in the way uncaptures are handled, of course only legal uncaptures are allowed. In Proca Retractors the retracting side decides, if and what man was uncaptured.
Anti-Circe Cheylan: After a capture the capturing piece (Ks included) must immediately be removed to its game array square (necessarily vacant, else the capture is illegal). Captures on the rebirth square are not allowed. Game array squares are determined as in Circe: R, B & S go to the square of the same colour as the capture; Ps stay on the file of capture; fairy pieces go to the promotion square of the file of capture.
Andreas Thoma presents a selection (PDF) of 5 Proca Retractors with Anticirce Cheylan condition, having the same idea. The diagrams are on the top of page, solutions on the bottom. For the competition problems numbered from No.1245.1 to 1245.5, publication date 28.10.2017.