Hey @djconnel, really enjoyed your post—great breakdown! 👏
You’re right about the math behind Chess960 (4×4×6×10 = 960)—and yeah, in some official tournaments, the standard starting position from classical chess is excluded, which does make it effectively Chess959 in practice. It's not part of the FIDE rulebook per se, but more of a tournament convention, likely to encourage players to prep for more randomised setups rather than just defaulting to what they already know.
Your point about the mirror position with king and queen swapped (aka Chess958) is fascinating—I don’t think that one’s officially excluded, but you’re right that it creates an interesting “almost standard but not quite” variation that sits in an odd grey area. It would be cool to know if that one is ever filtered out, too.
And YES, calling it “freestyle” is kind of funny when the whole point is that you don’t choose anything 😅 Your comparison to actual freestyle swimming is spot on. Honestly, I wouldn’t mind seeing a “true freestyle” variant where each player picks their back rank—chaos mode!
Anyway, great post—thanks for sparking such a fun reflection on naming, logic, and structure. This is exactly why I love chess variants!
There are 960 possible positions in chess960, which is of course why it's called chess960. You can calculate these positions easily: 4 possible for the dark square bishop, 4 for the light square bishop, 6 left for the queen, then there's 5x4/2 = 10 possible placements of the two knights (the divided by two is because the knights can be swapped without effect), then that leaves 3 squares which must be occupied R-K-R. So 4x4x6x10 = 960.
But in tournaments, I've seen the original position is typically excluded, so that leaves 959. I don't think that's in the basic 960 rules. I think it's just a tournament-level decision.
But the theory is identical for a mirror-image position, where the pieces are in the conventional positions but with king and queen swapped. Is this also excluded? I don't know. But that would be chess958.
It would be clearer if the name reflected how many positions were actually allowed.
Of course there's "freestyle chess", a reference perhaps to "freestyle swimming", but it's a misnomer, since in swimming the player chooses the stroke, while in chess960 the position is chosen for the player. There's nothing "free" about it. Imagine if each player could chose their initial position, commit it to a piece of paper, and then the game was played. That would be more "free".
There's also "Fischer Random" which is a fine name because there's specific rules which make it 960: the relative position of the king between the rooks, and the castling rules. Obviously castling could have been done differently, with the same rules for setting up position. That would have still been a "Chess 960" but not the Fischer version.