H. G. Muller wrote on Sat, May 15, 2021 10:16 AM EDT:
For now I disabled automatic W* -> nW* interpretation on all pieces except the first.
(As I think other diagrams would only use it for the first defined piece = Pawn.)
This enabled me to define the Ninja Pawn as non-e.p.-capturable.
The dependence of moveon the board half is taken care of a customized WeirdPromotion() routine,
which promotes Ninja Pawns to 'Ninjas' (represented by the same image) when they enter the opponent half.
For now I disabled automatic W* -> nW* interpretation on all pieces except the first. (As I think other diagrams would only use it for the first defined piece = Pawn.) This enabled me to define the Ninja Pawn as non-e.p.-capturable. The dependence of moveon the board half is taken care of a customized WeirdPromotion() routine, which promotes Ninja Pawns to 'Ninjas' (represented by the same image) when they enter the opponent half.
[Edit] Diagram was moved into the article.