[Retros] Circé cage

Nicolas.Dupont at math.univ-lille1.fr Nicolas.Dupont at math.univ-lille1.fr
Wed Dec 16 11:42:11 EST 2009

Hi Joost,

> What is the exact English definition of Circe cage?

You can read it page 11.

> Implementation question: Consider the following position:

> W: Ka2 Pg2

> B: Kg4 Ph3


> Popeye implementation says that e.g. g2xPh3[Pe6] is a legal move,

> because on e6 the pawn has no legal non-capturing moves. IMO this feels

> 'wrong', e6 doesn't feel like a cage. Is this type of cage intended by

> the inventors?

Yes. This is the special case when a capturing move gives check. This is
true that the concept of cage is rather abstract in that situation, but we
prefered not to invent a particular rule devoted to a checking capture.
See problem 5 for an illustration.


More information about the Retros mailing list