huh, I originally thought this would create unusually long URLs, but if it's just the sequence of moves it could stay pretty small.

might more fun too, representing each state of play instead of just the board position.

Also easily compressible if size is an issue: https://mbuffett.com/posts/compressing-chess-moves

Would also mean all rules can be represented, and you'd be able to do cool things like highlight the previous move that was made.

Nice, ok, might try and add this.