new fairy condition

[marioparrinello1960]

Hello Popeye's team,

I would like to introduce you a new fairy condition invented by me.
I think it is very dynamic and suitable for all genres of chess problems; I attach a recent short article of mine on this new condition published on October issue 2025 of Best problems.
I would highly appreciate your opinions and I hope you are interested in implementing it in your solving program.
Thank you in advance!

Best regards,
Mario Parrinello
new fairy condition.pdf

[thomas-maeder]

I have created feature request #586 from this discussion.

[thomas-maeder]

In your document, you use the term "where the capture occurs". What does this mean for moves where the capturing piece doesn't end up on the square previously occupied by the captured piece, e.g.:

• en passant capture
• capture by Locust
• Anticirce
  ?

[marioparrinello1960]

Good point! Unfortunately I did not take into account all possibilities and/or combination with other fairy conditions/pieces...Obviously, there are as many other unexplored possibilities as there are fairy pieces/conditions...
Anyway what I would suggest is as follows answering your specific objections:

-en passant: consider this position White : Pe2, Pf2--Black : Pf4. After 1.e4 fxe3 e.p (bpe3<->wPf2)

-Locust capture: consider this position White LOg2---Black Pd5, Ph6.
1.LOxd5-c6 (LOc6<->bPh6)---I would suggest that Locust exchanges its place from the landing square (here c6)

-AntiCirce capture: White : Sg6---Black : Sh3 Pe5
1.Sxe5 (Sg1) (wSg1<->Sh3)
I would suggest that after completing the AntiCirce capture, the exchange phase involves the AntiCirce rebirth square (g1) and the exchanging one (h3)