Single Comment

that initial legs would behave differently from only legs.

The behaviour is the same if you stipulate that all slider legs are potentially 0‐length but null moves are disallowed unless explicitly specified

Perhaps we have different intuition

May well be :) And fwiw I'm fine with either system in practice

When 0 steps is allowed, you would need [F-fF-fB] for the Tamerlane Picket

Or simply [nA-fB], which to me looks more natural as an alfil extension (istr Gilman classes it that way too). [F-fB] is ofc a bit odd as a Bishop description, but there are always going to be strange ways of notating things

BTW, [W?sfNN], and even [W?sfCC] work now. All through using a new, undocumented (and quite horrible) extension of XBetza.

That's pretty cool :) (and agreed, the repeating ys are… not pretty). I can even get an offset giraffe‐rider (or even zemel‐rider — presumably longer ones work too, if they'd fit on the board), even though normal giraffe‐riders (FXFX?) are apparently unsupported!

But the y extension still fails for e.g. [W?sfZZ] (also shouldn't that be fsNN ⁊c?), let alone pathological things like [C?fsZZ], so if we're making an effort to support direction‐type changes it probably deserves to be more general.

Also speaking of the Z, [Z?sfB] currently gives me Zebra‐then‐Rook, and vice‐versa