It is just a variant of the Xiangqi King-staring rule. In this case it is illegal to have the royals see each other throug a W or N move, rather than an R move. In XBetza I would configure it as a kWkR move on both King and Fool. The Fool is an (extinction) royal. (And since there will never be more than one King, the latter could be considered an extinction royal too.) The white majors are subject to a baring rule (and the Diagram's AI would allow you to specify which piece types participate in the baring). I guess the Diagram could give an almost perfect implementation of this variant with the aid of a user-supplied JavaScript routine BadZone() to outlaw Fool capture by most piece types, and switching off the checking rule. The only imperfection then is that some stalemates would be seen as a win for black.
I am a bit worried about the promotion rule: can white promote only to Fool, or is this just an extra possibility? The Fool is practically useless as attacker, similar to an Elephant in Xiangqi. That they are uncapturable and that you can have many cannot compensate for this; N times zero is still zero. The possibility for white to win an end-game seems bleak if he can only promote to Fool.
It is just a variant of the Xiangqi King-staring rule. In this case it is illegal to have the royals see each other throug a W or N move, rather than an R move. In XBetza I would configure it as a kWkR move on both King and Fool. The Fool is an (extinction) royal. (And since there will never be more than one King, the latter could be considered an extinction royal too.) The white majors are subject to a baring rule (and the Diagram's AI would allow you to specify which piece types participate in the baring). I guess the Diagram could give an almost perfect implementation of this variant with the aid of a user-supplied JavaScript routine BadZone() to outlaw Fool capture by most piece types, and switching off the checking rule. The only imperfection then is that some stalemates would be seen as a win for black.
I am a bit worried about the promotion rule: can white promote only to Fool, or is this just an extra possibility? The Fool is practically useless as attacker, similar to an Elephant in Xiangqi. That they are uncapturable and that you can have many cannot compensate for this; N times zero is still zero. The possibility for white to win an end-game seems bleak if he can only promote to Fool.