This is sqAree from Berlin, first of all I want to say hi to the aagenielsen/World Tafl Federation community. Many thanks to Hagbard for running this great playing site and to nath for introducing me to the tafl game.
I personally like the Copenhagen variant a lot and can see its advantages over other tafl variants (of course it's also a matter of taste). Having said this, there have been more and more dicussions about the rules in the small chat lately and I'd like to contribute to the game by taking part in them.
I will refer to the rules as described here: http://aagenielsen.dk/copenhagen_rules.php
. Please note that I haven't read every single post in this thread, just point out if I write something that contradicts earlier posts. As for the translation I recently offered: I will work on it as soon as we settled on some final formulation of the rules.
Alright, let's get right into it:
I think rules 1,2,3,5,6 are well worded and need no further reconsideration.
About rule 4:
Contentwise fine, however it's a bit confused regarding redundance with rule 8. As there are multiple ways to win the game (for either player) we should possibly structure them so that no longer incoherent winning conditions for both parties are within one rule. Furthermore we might consider rearranging all the rules in way such that we have:
(A) Definitions and preparation (covered by rules 1,2,3).
(B) Moves and overall game mechanics (covered by rules 5,6,7 and also the first part of rule 8).
(C) Goals of the game respectively winning conditions (covered by rules 4,8,9,10). I know, usually (B) and (C) are transposed, but here the move mechanics are mandatory for the explanation of the winning conditions.
I'd suggest to start with the white winning conditions (corner escape and edge fort), proceed with the black winning conditions (king capture, drawfort and encirclement, although the latter possibly will become dispensable as a consequence of the eventual immobility rule and is only there to finish a game faster) and conclude with general outcome rules (immobility and perpetual repetition).
About rule 7:
At first I'd like to know a definition of "taflmen". Nath recently told me that the king cannot be captured by the shieldwall capture (which is consistent as otherwise a single king could die by being bracketed between 2 attackers on the edge), so there's something wrong here: Either "taflmen" are "attackers, defenders and king" or "attackers and defenders". However, the king may participate in the "shieldwall" but not as a "victim".
Of course we could rework the definitions now, but I simply suggest to add below: "The king may take part in the capture, either as part of the shieldwall or as the bracketing piece. The king cannot be captured using a shieldwall."
About rule 8:
Again contentwise fine, just the same as for rule 4, maybe split and rearrange. If immobility becomes a rule of its own, incirclement may stay as a special case (with the pure reason to shorten games as should be mentioned).
Also I wonder if the immobility rule has any significance in respect of a black loss. If black is indeed immobile, it seems that white can easily achieve a corner escape or an edge fort, because white has too few pieces to block every black piece in case the corners are secured.
What about this position (king:f11,black:e11,e10,f10,g10,g11,h11,white:d11,d10,e9,f9,g9,h10,i11). According to immobility white would win even though his king is surrounded. Of course white has a trivial win anyway by moving a piece, putting black into zugzwang and finally escaping with the king.
That makes me think of the following position (king:f11,black:d11,e11,f10,f9,g11,h11,e10,g10,g9). The king cannot move, fine. The black structure can never be captured, also fine. Now we distinguish between several cases (initially taking no account of loss by repetition of position):
Case (a): White doesn't have additional pieces. --> Undeniably black wins with either player to move, according to immobility.
Case (b): Black has no additional pieces, white has no more than 7 additional pieces. --> White cannot encircle the black pieces, so black will never be immobile. It's perhaps possible to put black into zugzwang but I guess white would lose pieces without uncaging his king then. That means, white would maybe win the game although his king certainly will never reach a corner or an edge fort.
Case (c): Black has a few additional pieces, white has no more than 7 additional pieces. --> As long as black's additional pieces don't get trapped, neither player can accomplish anything.
Case (d): Black has no additional pieces, white has enough pieces to encircle the black structure. --> This is an easy one: White blocks black and wins again by immobility despite his king being trapped.
Case (e): White has encircled the black structure, but black has additional pieces outside. --> 12 white pieces are not sufficient to savely block the black structure without losing pieces if black has enough additional pieces. But, say, black got one piece (beyond his 9) and white as well (beyond his 8). Black continually tries to threaten the black heap but the one defender is always preventing a capture.
A funny position would be (king:f11,black:d11,e11,g11,h11,j11,e10,f10,g10,h10,i10,f9,g9,white:c11,d10,e9,f8,g8,h9,i9,j10,j9). Black would be immobile if he hadn't constructed a black fort.
I will take up on this later.
About rule 9:
As earlier mentioned in this thread, consider a position where white's only piece is the king and black has secured all corners using 3 pieces each. Technically white would win, if the king has contact with the edge, because he is able to move and cannot be captured really. Well, as for this rule I do understand how it is supposed to work, it's just the wording that is ambiguous in my opinion. We would need to clarify if it's "impossible for the attackers to capture him in the next move" or "impossible for the attackers to capture him in the course of the game" or "impossible for the attackers to capture him after any amount of moves assuming that white passes all the time". Of course only the latter would be right and it's also my suggestion for a reformulation, because when reading the actual rules as is, every of the above interpretations could come to one's mind.
However, there is still an issue, namely the cases where the king is part of the fort structure, because this situation is supposed to be a black win. My final suggestion for a reformulation is as follows: "The defenders win if the king has contact with the board edge, is able to move, it is impossible for the attackers to capture him after any amount of moves assuming that white passes all the time, and it is impossible for the attackers to render white immobile assuming that the king is forced to move at least once."
I hope this is correct. Anyway, it's anything but descriptive, so an alternative would be: "The defenders win if the king has contact with the board edge, is able to move, and it is impossible for the attackers to win the game if they control their pieces plus the king while the defenders don't move."
At least this would save us defining precisely what an edge fort essentially is.
In any case I recommend adding a few more examples of edge forts. Really, not a single formulation of rule 9 is intuitively accessible so far.
About rule 10:
To start with a few questions:
(Q1) Does this rule apply for both players?
(Q2) If yes, who is the "threatening player", how is he determined?
(Q3) Is this a sudden death or is the move that would lead to the repetition just banned? (of course the answer doesn't matter as in case of no sudden death the immobile rule would do the job)
My further reasoning will depends on the answers. I think, this is the point where it comes down to defining what copenhagen Hnefatafl is all about.
Everyone would agree that white's goal is to let his king escape to a corner. Now what should black's goal be? It can be "capture the king" or the contradiction to white's goal.
Given that it's the former, the idea of forts pops up immediately: A white structure that can live autonomously prevents the king capture. If I recall correctly those forts are counted as draws in Fetlar Hnefatafl which is quite reasoned; neither player can reach his goal. Now we distinguish between edge forts and usual forts, probably because reaching the edge is somewhat more of an escape then a draw fort in the centre of the board. Alright, so edge forts win for white and other forts should be truly worse. It can't be a draw though because white would have a trivial draw from the starting position then. Concluding the non-edge forts count as losses for white.
So far, so good, this was just a small recapitulation of what I think the chain of thoughts was when designing copenhagen tafl.
Now let's pose this question once again: What should black's goal be?
Let's say it's "capturing the king". --> Corner escape (white win), king capture (black win). Edge fort (white win), but draw fort (black win)? Both of the forts accomplish two things, that is, preventing the king from being captured and getting rendered immobile. In this case both forts should count as a draw actually, because no player has a chance to reach his goal. Even if we put edge forts aside; there are still cases where black simply can't win by capturing the king, but rather by encirclement. Not to mention the positions I described under rule 8.
What if black wins by ensuring white doesn't reach his goal? Would be my first choice when designing a game, because it just sounds too logical. Note that there is no contradiction to any of our working copenhagen rules; every case that is covered by them would have the same outcome under this assumption.
Now we have cases (b), (c), (d), (e) (see my comment for rule 8) as well as the case where black has secured each corner and both players have very few pieces left (as described in the small chat, let's call it (f) for references) plus maybe the black fort (g). Let's now start applying the gathered points and rule 10 to those cases:
(b) No matter if white got at least 4 attackers or not, the outcome will be decided by which player goes out of non-repetetive moves first (assuming Q1 is answered yes). Since black has no additional pieces and needs to sustain his structure, he will most likely lose.
(c) Actually the same as (b), the outcome will depend on Q1 and the number/arrangement of each player's pieces.
(d) Nothing would change, it's still a white win. I find this kind of counterintuitive though.
(e) Again the outcome depends on Q1. If only white is not allowed to repeat positions, it's a black win. Otherwise Q2 gets interesting.
(f) Technically white would lose according to the draw fort rule if he has at least 4 defenders and can't build an edge fort. But it might take so many moves that it's impossible to finish the game in practice. If he has 3 or less defenders, maybe the perpetual repetition would be effective eventually (Q1,Q2).
(g) Black can only move one piece back and forth. Once again Q1 and Q2 will decide.
So, quite a lot depends on Q1. If the answer is "yes" the example positions are a mess to deal with, because the result will almost always be revealed only after a long time. And even if we decide to allow draws (it's still not in the rules and admittedly I'm against draws) there remains a lot of work to decide the outcome arbitrarily for those border cases. That's why I propose to make it possible only for white to lose to the perpetual repetition rule. Of course this can be abused in the midgame by repeatedly threaten the king and winning as black without capturing him. But I think this might actually be a nice tactic.
So, let's look how the cases behave under this ruling:
(b) Black wins if he manages to uphold his structure. Success might be difficult to prove, but not impossible. I believe that white wins comparatively fast if he has a win, so an "after x moves black wins"-rule could help to detect the outcome. In chess it's standard that the umpire sets a match's result if one player does not try to win (in his opinion). Either of those rules could be applied here.
(c) Black moves his other pieces and wins because white will have to repeat a position at some point. Seems fair to me. Get a referee to end the game faster.
(d) Although this seems counterintuitive it's not really arguable that it's a white win. This might be the only situation where white does not win reaching one of his main goals. Though as if this position will ever occur anyway..
(e) Would be a black win analogous to (c).
(f) Nath mentioned this somewhere in the small chat. If white has 3 or less defenders, he loses (just a shortcut for the perpetual repetition rule). If he has 4 or more, however, I can't see how black can secure every corner and let at a max 2 squares per edge for white while he has too few pieces to win the game.. Let's just say, analogous to (c) and (e) white loses after a fixed amount of moves (he should get a chance to build that edge fort at least) or if an umpire decides so. I am deeply convinced that it should be a black win, because white hasn't accomplished anything: No corner escape, no edge fort, no encirclement of black pieces.
(g) Interestingly this would be a black win, obviously. The black fort's charme is quite decreased because now he wins in the other cases as well. What a pity..
All in all, it seems like a rule analogue to the Fifty-Move-Rule in Chess (maybe a different number, depends on how many moves it will usually take to build an edge fort, and a black win instead of a draw) would resolve all cases. I agree that chess is a bit flawed because there are positions that would be a win without the Fifty-Move-Rule, check http://en.wikipedia.org/wiki/Chess_endg ... forced_win
, a position with white to play and force mate in 549 moves. Then again we have endgames like Bishop and Knight against King that win within 50 moves but it's okay to punish a player if he fails even once. We might want to compute a number x, such that an edge fort - if possible - can always be built in x or less moves.
Alright, I was writing for hours and am extremely tired, but I said anything I wanted to say - for now. I guess my text will be flawed as hell, please bear with me, I'm only a beginner.