No.719,720 (CJF)

Two problems by Chris Feather:

• No.719 – A very interesting play of white Pe2! ;
• No.720 – White Excelsior combined with surprising black self-blocks! (JV)

Definitions:

Nereid (ND): (1,1) Marine. Marine piece operating along Bishop lines: without capture moves as Bishop, with capture – as Locust.

Bishop-Locust(LB): Moves like Locust, but on Bishop-lines only.

Locust(L): Moves along Queen lines only by capturing an enemy unit, arriving on the square immediately beyond that unit, which must be vacant.

Symmetry Circe: As Circe except that the rebirth square for the captured unit is that which lies at an equal distance (in a straight line) beyond the midpoint of the board. Thus a capture on c4 produces a rebirth on f5, a capture on g1 produces a rebirth on b8, and so on. Strictly speaking there are of course other types of symmetry: this one is rotational. (Or from Fairings No.42: Captured units are reborn on the square which lies at an equal distance (in a straight line) beyond the midpoint of the board. If the rebirth square is occupied the capture is normal.)

Diagram Anti-Circe: When a piece captures (including King), it must come back to its rebirth square (the square it occupied in the diagram position): if this square is occupied, the capture is forbidden. A Pawn capturing on its promotion rank promotes before it is reborn. (Or from Fairings No.42: As Anti-Circe except that the rebirth square for the capturing unit is the one where it stands in the diagram. In the Cheylan sub-type a capture by a unit on its own rebirth square is not allowed.)

Diagram Circe: When a piece is captured (King excluded, unless otherwise stated), it must be replaced on the square it occupied in the diagram position if it is empty; otherwise, the captured unit vanishes.

Circe: Captured units (not Ks) reappear on their game-array squares, of the same colour in the case of pieces, on the file of capture in the case of pawns, and on the promotion square of the file of capture in the case of fairy pieces. If the rebirth square is occupied the capture is normal.

Anti-Circe: Anti-Circe Calvet (the default type): 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 allowed. Game array squares are determined as in Circe. Anti-Circe Cheylan: As antiCirce Calvet except that captures on the rebirth square are not allowed.