Author Topic: Peace Chess (Paco Shako)  (Read 101 times)

HGMuller

  • Global Moderator
  • Full Member
  • *****
  • Posts: 122
    • View Profile
Peace Chess (Paco Shako)
« on: February 02, 2018, 08:03:59 am »
Rules

One of the most innovative Chess variants I ever encountered is the recently invented 'Peace Chess'. This variant has changed the general rules for capture, which in orthodox Chess symbolizes a fight in which the attacked piece dies, to a peaceful coexistence of the two pieces on the target square, embracing each other. Of course this prompts the question how to handle such embracing pairs in the remainder of the game: what happens if a third piece now 'captures' to a square already occupied by an embracing pair? The rules specify that in that case the third piece entering the square replaces the piece of the same color in the embrace, and the replaced piece then has then to move away in the same turn. Such a released piece can do everything a lone piece could have done, in particular it can again release pieces from another embrace, which then has to move away, etc. So you can get arbitrarily long chains of moves in a single turn.

The embracing pairs can also be moved, as their component pieces, except that they can only move to empty squares. This means both players can move them, but if (say) a white Queen is embracing a black Knight, white can move the pair as a Queen, and black can move it as a Knight. In all cases they would move as a pair: the Queen would drag the Knight along, the Knight would drag the Queen along. So there is no way to break an embrace once it is formed, although you can substitute one piece in the embrace for another.

He who first embraces the opponent King wins the game. As all pieces always stay on the board, be it as lone pieces or tied up in an embrace, stalemate is a moot point. In real games it just never occurs.

Strategy

My first impression, when confronted with these rules, was that a game like that would never end, and just muddle on, because pieces are never removed from play. It was not clear to me how you could make progress, or even how progress should be defined. The number of embracing pairs can only increase during the game, losing the ability to capture, and in particular to embrace the King. So it seemed to me the game would just peter out before there was any danger to the Kings. I could not have been more wrong...

Embracing pairs are actually quite dangerous. Because they act as 'amplifiers' for the lone pieces. E.g. an embracing Queen on the target square of a friendly Knight doesn't block a move of that Knight (as a lone friendly Queen would have done), but allows the Knight to release that Queen from the embrace, and do a follow-up Queen move. So it is as if that Knight gets one of its moves replaced by all the moves of the Queen. So embracing pairs are far from 'dead wood'. You should be prepaired for the pieces in there to be released at any time, able to engage in new embraces.

As there is no limit to the length of release chains, the releases can also occur indirectly. E.g. an embracing Knight could be a Knight jump away from an embracing Queen, and when a lone Rook now releases the Knight, that Knight can release the Queen. So 'virtual attacks' of a piece tied up in an embrace on another embracing pair are potential ways to propagate a release chain to a distant piece, and release that from its embrace. And the more emracing pairs there are on the board, the more often pieces in such a pair will happen to have such virtual attacks on other pairs. If they virtually attack more than one other pair, a release chain reaching them would branch there, to continue along two different paths.

As is the nature of branching chain reactions, at some critical density of embracing pairs the point will be reached where the average number of virtual attacks per pair will surpass 1. Then the number of possible chains will 'explode', and it will become possible to make almost any piece appear from an emracing pair anywhere, even from a pair it wasn't originally in. To illustrate this, look at the following simplified example:

8 . . . . . . . .
7 . . . . . . . .
6 . . . . . . . k
5 . . . . . . . .
4 . . . Rp. Rp. .
3 . . . . . . . .
2 . Q . . . . * .
1 . . . . . . . .
  a b c d e f g h


where the Rp indicates a white Rook embracing a black Pawn. White to move can play (all in one turn) Qxd4, Rxf4, Rxd4, Qxf4, Rxd4, Rxf4, Qxh6#. Because the embracing Rooks are virtually attacking each other (i.e. on average 1 virtual attack per pair, on the edge of criticallity, so you get an infinitely long chain, but it doesn't branch yet), they can be used as relay points for other pieces. They can bounce the release 'activation' around and make it return to where it came from, reactivating the piece that 'lighted the fuse' for another move in the same turn. Thus allowing it to hop from relay point to relay point. Each embracing piece virtually attacking a relay point automatically becomes a relay point itself. E.g. if there had been an embracing Knight on g2 (virtually attacking Rf4), it would have been able to act as a relay for the Queen to move to, say, h1: Qxg2, Nxf4, Rxd4, Rxf4, Nxg2, Qh1! The Queen doesn't just have her own moves from b2, but can appear from d4, f4 and g2 as well. It is as if every embracing piece has become a lone Queen (in addition to g2 being able to come out as a Knight as well).

Of course embracing pairs can also be moved by the opponent, who will try to break your most dangerous chains by moving them out of virtual-attack. But if the density of embracing pairs increases, it will get progressively more difficult to do that without creating new virual attacks. In addition, he might not have the possibility to move them. This in particular happens when his piece in the embrace is a Pawn, as a Pawn only has a single move (an embracing piece cannot capture!), which could easily be blocked. This shows it is particularly favorable to have your strong pieces embracing opponent Pawns; then you can rely on them to stay where you want them to act as relays. This leads to the paradoxical situation that capturing a Queen with a Pawn is a quite poor move!

As the density of embracing pairs increases during the game, the attacking power of both players will be more and more amplified. So that the advantage to have the move becomes larger and larger. Usually the point where your attacking power gets so large that the opponent cannot protect his King from embrace in the next move anymore, is reached long before all pieces are embracing.

Equipment



Peace Chess can be played with a set of normal Chess pieces, but it is a bit awkward to cram two such pieces on the same square. The inventor of Peace Chess (Felix Albers) now sells a very nice set of Chess pieces especially designed to embrace each other on a single square. Some of those pieces can be seen in the photograph above. Looked at from the bottom, such an embracing pair looks like the Yang-Yin symbol!


« Last Edit: February 02, 2018, 09:27:28 am by HGMuller »

Share on Facebook Share on Twitter


John_Lewis

  • Newbie
  • *
  • Posts: 47
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #1 on: February 02, 2018, 11:15:48 am »
Just to clarify;

  • You can't combine your own pieces.
  • The combined piece has the powers of both previous pieces.
  • Combining with an already combine piece activates the previously combined piece of your color and that piece can move... what is the notation look like for such a move?
  • It's possible to mate yourself by combining your King with an adjacent opposing piece, but does this result in a draw if you then bounce your own piece into the opposing King?

Thanks, this looks very interesting, particularly the physical pieces.

HGMuller

  • Global Moderator
  • Full Member
  • *****
  • Posts: 122
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #2 on: February 02, 2018, 11:43:58 am »
1) Indeed. Moving to a square occupied by a lone piece of your own, is forbidden (like in orthodox Chess). You can move lone pieces only to empty squares or squares that contain a (paired or lone) opponent piece.
2) Yes, in the sense that you never were allowed to move your opponent's pieces in the first place. So my Rook embracing his Knight can be moved in my turn like a Rook, but not like a Knight, as the Knight cannot move in my turn.
3) Well, a simple notation that works in general for variants where multiple pieces can be moved in one turn would be to just separate the individual moves by commas. It might be more clear if a released piece would always be followed by an asterisk as a disambiguator, like R*xf4.
4) The current rules stipulate that the King can never initiate an embrace, i.e. instantly loses when he does, without completing the move for any pieces he released. This makes the King quite defenseless, however, and unprotected Queen can drive it to the edge for checkmate. So rule modifications to improve the King's defense are under study. Allowing the King to embrace on its own initiative (also after release) is in itself not a solution, as this would allow the opponent then to 'abduct' the King by retreating the embracing pair deep into its own camp, where it would not survive anyway. So it would only work in combination with a rule that forbids moving a piece that was embraced by the King. This complicates the rules, however.
« Last Edit: February 02, 2018, 12:07:24 pm by HGMuller »

John_Lewis

  • Newbie
  • *
  • Posts: 47
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #3 on: February 03, 2018, 02:50:06 pm »
1. This makes sense.

2. Oh! I thought you could move the piece as either of the combined pieces as could your opponent. Is there currently a rule regarding repetition of combined pieces? A combined Queen/Rook moving back and forth with checkmate unattainable?

3. Yes, the chained movement is what I was curious about. My pawn releases my bishop which then releases my rook ... the notation quickly ends up looking odd if you don't have some way to show the chaining. Example of chain notation:c2xb3>Bb3xa2>Ra2xa4

4. So currently the rule could be simply that if the opposing King is embraces, you immediately win. Wouldn't matter who initiated it, resolves strange combinations.

HGMuller

  • Global Moderator
  • Full Member
  • *****
  • Posts: 122
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #4 on: February 03, 2018, 04:39:17 pm »
As to (2), the current rule doesn't forbid undoing the move of your opponent, if the piece types in the embrace allows that. In human games this doesn't seem much of a prblem so far, but a simple demo AI I made for on the website seems to have a tendency to repeat positions. (Probably also because I did not put in code to make it recognize that as a draw.) So another rule change under study is to forbid moving a pair that the opponent just moved.

John_Lewis

  • Newbie
  • *
  • Posts: 47
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #5 on: February 04, 2018, 04:49:01 pm »
There's a little bit of Alice Chess in this (in that you can both be in the "same square" in Alice Chess) but the joining of the pieces is quite nice. I like the phrase "embrace" very much for describing the mechanic. It's like a friendly hug and oh, let's go move some place you don't want to be for awhile.

It would seem to me that the Knight would increase in value for such a game because it can "kidnap" an opposing piece and place it in hard to reach location after leaping... trapping it. Since an embraced piece can't move into an occupied space, you can safely embrace the opposing Queen and then move it behind your own lines where your opponent is stuck and can't move out.

Edge case questions:

A. En Passant, does it still work and if so where does the embraced piece end up?
B. Embraced pawns reaching the last rank, are they effectively stuck there or do they promote? Can they promote on the opposing players turn?
C. Is castling blocked by opposing pieces attacking a square between the Kind and Rook (embraced or not)?
D. Can an embraced Rook still castle if it has not previously moved?
E. When you embrace a pawn to an opposing piece, if you later dislodge it can it choose to either embrace diagonally or move? I'm assume it can't "move" into a square occupied by an opposing piece.

HGMuller

  • Global Moderator
  • Full Member
  • *****
  • Posts: 122
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #6 on: February 04, 2018, 05:17:38 pm »
That is a useful strategic insight, about the Knight. I would like to build an AI that can play this, in oder to test rule variations (e.g. how they affect draw rate). But it is very hard to make an evaluation function; I simply don't know what one should strive for when embracing the opponent King is not within the horizon.

As to your questions:
A) The rule book that is delivered with the pieces describes e.p. capture as moving back the 'captured' Pawn one square to embrace it, and then move the now released piece from the square it was. This strikes me as illogical, as there isn't any need to move the released piece. A more logical way would move back the entire pair to the square it skipped, and then perform the capture as normal. It probably wouldn't affect the game much whether you do one or the other.
B) Pawns reaching last rank promote, even if the opponent dragged them there. The most practical way to do this in a timed game is to just press the clock after you dragged the Pawn, so the opponent can (and must) decide what to replace it with in its own time, in additio to playing his normal move.
Note that Pawns can also be dragged to first rank. They will have a double-push from there, which would be subject to e.p. capture.
C) Indeed, Kings should not travel through squares that are under real attack (by a lone piece, or through a chain move).
D) It doesn't matter whether the Rook is paired (although it might not be a good idea to put your King next to a pair).
E) Indeed, only diagonal Pawn moves can embrace (possibly triggering a release). Moving straight forward is only possible to empty squares. So an embracing Pawn can very easily be blocked, and can then neither be released, nor move the entire pair. It is forbidden to move into an embrace when the released piece would not have a place to go.

Greg Strong

  • Newbie
  • *
  • Posts: 21
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #7 on: February 04, 2018, 06:29:33 pm »
There's a little bit of Alice Chess in this (in that you can both be in the "same square" in Alice Chess) but the joining of the pieces is quite nice.

Actually, that's not quite true.  The rules of Alice Chess are such that the two corresponding squares of a pair can never be occupied at the same time.  (You could, for example, play on a single board where some pieces sit on top of checkers pieces or not to designate which "phase" they are in.)

John_Lewis

  • Newbie
  • *
  • Posts: 47
    • View Profile
Re: Peace Chess (Paco Shako)
« Reply #8 on: February 06, 2018, 08:52:16 pm »
There's a little bit of Alice Chess in this (in that you can both be in the "same square" in Alice Chess) but the joining of the pieces is quite nice.

Actually, that's not quite true.  The rules of Alice Chess are such that the two corresponding squares of a pair can never be occupied at the same time.  (You could, for example, play on a single board where some pieces sit on top of checkers pieces or not to designate which "phase" they are in.)

Interesting, I've played they could occupy the same "space"... on the other board. This was obviously easier with a computer taking care of the movement.

We also had variants for White starting on one board and Black starting on the other board, which I found more fun.