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Fusion Chess. Variant in which pieces may merge together or split apart. (8x8, Cells: 64) [All Comments] [Add Comment or Rating]
Fergus Duniho wrote on 2020-03-07 UTC

> It would need some rule that you cannot move a royal slider through check, like in Caissa Brittannia, to make it a serious game.

Since I was just thinking of another rule I wanted to change, I opened my .zrf file for this game to see how I could make the change. When I did open it, I noticed that I made some rule updates in 2006, but I never changed the rules on this page. One of the rules was the one you suggested here. Here are my comments from the .zrf file:

; *** Rules changed in February 2006
; *** King cannot initiate fusion.
; *** Simple pieces may initate fusion with King.
; *** Dragon King and Pope may not move through check.

As the rules are currently written, the King may initiate fusion, but another piece may not initiate fusion with the King. Two of the rule changes above reverse this. This might be to prevent the King from using fusion to get out of check.

The new rule I'm thinking of adding limits the use of fission for getting out of check. I initially thought of just forbidding fission for getting out of check, but it seems simpler to forbid fission by a piece that is currently attacked. This prevents the two ways fission could be used to get out of check that would tilt the advantage in favor of defense. One is if a royal compound piece is in check, and the player splits off the non-royal component to block the check. The other is if a pinned piece is blocking one check, and it splits off one of its components to block another check. This is more permissive in some ways and more restrictive in some ways than the other condition I thought of. It is more permissive, because it allows a check to be blocked by splitting apart an unpinned piece. It is more restrictive, because it does not allow any attacked piece to split apart.

Its main advantage is that it will require less overhead. In Zillions, I can just add "not-attacked?" to the appropriate code, and in Game Courier, the legal fission moves will all correspond with other legal moves, which eliminates the need to write extra code for calculating possible fission moves. Since that advantage would be lost if I used both conditions, I will just use the simpler condition. So, the rule I'm thinking of adding is that it is illegal to split apart a piece that is attacked.

I am currently in the process of programming a Game Courier preset for Fusion Chess. When I have finished with that, and when I have updated the Zillions file, I'll officially update the rules.