This could be extended into an "ultra strong copenhagen" where three types of repeated board positions are identified like this:Adam wrote:I am beginning to lean towards an 'extra strong copenhagen', whereby all repeated board positions become illegal on the third repetition, with the exception of a mobile king edge fort exit, which results in a white win.
rule+3. The overall board position may be repeated no more than three times (except for the white win edge fort exit - which isn't really a repetition as the game has ended). The player who maintains the situation ("the threatening player") must find another move to break the repetitions.
rule+3a. The white board position may be repeated no more than three times. White must find another move to break the repetitions.
rule+3b. The black board position may be repeated no more than three times. Black must find another move to break the repetitions.
rule+3 covers the intertwined perpetual step dance of any complexity, three times around the board or whatever.
rule+3a covers white draw forts where it's white alone who does the repetitions.
rule+3b covers fx. the situation where black just barely blocks all corners. A repetition ban forces black to leave the corners, and the game will end a draw because of lack of white and black pieces.
If very much needed, the corner squares could be friendly to the king?Adam wrote:Though I hasten to add that if that includes corner capture [of the king] with two men and a corner refuge, then I'd consider this a rather severe handicapping.
This might be an idea anyway, because it is the neighbour corner square safe for the king which is the source of a lot of the interesting combinations and quick and elegant king exits, which are so characteristic of Fetlar. It is not very important for these fine combinations whether the king is safe on rest of the edge, too.
The German Trebeta reenactment group had a Hnefatafl rules set with the kings' squares friendly to all whites and the king. This looks like a drawback for the battle, as it spoils the corner fights. But friendly just to the king and only corners?
By the way all these rules adjustments address draw situations in the end games. 90% of the Copenhagen games turn out to be pure Fetlar games and are unaffected by the draw-adjustments.
Only with the exception of the innovation "white win edge fort"; and a removal of the special Fetlar edge rule also affects the game.
I found again the folder with the Scandinavian Museums' Skalk Hnefatafl rules. In the end of the text it says:
"White wins when the king succeeds in escaping to one of the corner-squares. Here he is free and invulnerable." Period.
"Black wins by taking the king. ... Black has also won if the situation arises that all white's pieces have been rendered immobile by encirclement."
They could be thinking of all these situations:
In which case this rule from Skalk covers rule+1, rule+3a and rule+4 of this discussion.