The l and r modifiers are relative to the player, so it seems I need the ability to specify a different betza for white and black.
You can specify an extra parameter castleFlip=1 in the Diagram to swap the meaning of l and r on castlings.
I am not entirely happy with that; I guess a neater solution would be to apply the l <-> r swap on all of black's moves. And perhaps this should be applied automatically based on the specified symmetry (none, mirror, rotate), where mirror then should do it, and none / rotate not.
You can specify an extra parameter castleFlip=1 in the Diagram to swap the meaning of l and r on castlings.
I am not entirely happy with that; I guess a neater solution would be to apply the l <-> r swap on all of black's moves. And perhaps this should be applied automatically based on the specified symmetry (none, mirror, rotate), where mirror then should do it, and none / rotate not.