The passing-through-slider-check should be fixed now. (For accepting the move. It is still highlighted. And it still gives this strange error message when you try it illegally.)
If castling were working, would that also mean a king would be unable to make an initial leap to escape check?
This is not an automatic rule. Should it be one? I could designate the origin of an initial move by a royal always an e.p. square, and that would then enforce this rule. But I don't know if the rule is universally valid.
The passing-through-slider-check should be fixed now. (For accepting the move. It is still highlighted. And it still gives this strange error message when you try it illegally.)
This is not an automatic rule. Should it be one? I could designate the origin of an initial move by a royal always an e.p. square, and that would then enforce this rule. But I don't know if the rule is universally valid.