Ratings & Comments

I corrected the name and removed some dead links. This page would benefit from an update. If you're interested in providing a better page with better and more detailed graphics, you're welcome to.

It appears this game is not on Richard's PBM server by any name provided. So, I removed that link.

I came on this page by accident. After so many years, the name of this game is still wrong. It is Doushouqi, not Shou Dou Qi at all. And the comment about jaguar for leopard is absolutely right. The solution to avoid a L is to call this piece a Panther, panther or leopard is the same animal.

Actually, I agree with the idea that one page more or less per person makes a noticeable difference. I meant literally 1 page, kept for the specific comments and discussion, done by the few people who do wind up with a separate revised version. And it's kept for the discussion.

It's a personal thing with me. I hate seeing information lost. I argued with everyone from John Smith to Derek Nalls about deleting games. I lost both those particular arguments, and lament it. Both had interesting stuff that they later decided didn't live up to their standards.

But I admit to being surprised at how many game courier settings files I have. Some of them can go, being early attempts at something I did better or gave up on. Some are non-chess prototype designs used for playtests of other people's games. Game Courier can handle a lot of abstracts besides chess variants. Should they go, too?

One page more or less won't make that much difference to this site.

I completely disagree with this.  Yes, there is a lot of clutter that should be cleaned up.  And, from time-to-time I do make progress on that.  But step 1 is not to make the situation worse.

Patience. I will get to changing the name.

I haven't been following this conversation, but I was in the same situation. Create the revised game using the new name but put links into it to the original page, and edit the original page to link to the revised rules, with notes that the original is being kept for the history and comments. One page more or less won't make that much difference to this site. And you haven't disappeared all that work.

I have just edited the rules. I split them up into more numbered items, and (I hope) added clarifying language. Thank you for the comments and questions. Please take another look.

I am still pondering the question of the name. If I change the name, will the URL change? And if so, would we lose these most excellent comments?

Thanks.

Ted

That's a great suggestion! I might be more inclined to "Two Move Chess", but I like it either way. Thanks for the suggestion.

Okay, let me see if I can explain my thinking here. The terms "turn" and "move" are not interchangeable in this game. The rule for stalemate could be stated most simply as: the game ends in stalemate if at the start of a player's turn he is not in check and cannot complete a legal turn.

To break that down, assume that the player is not in check. At the start of his turn the game is in one of two states:

1. His opponent has just made a single move. In this case he must make a response move. Since this is just one move, the possibility of stalemate is evaluated exactly as in international chess.
2. His opponent has not just made a single move, so he may take a two-move turn (if possible) or a single move turn (if possible). Keep in mind that the set of moves that could comprise the first move of a two move turn is disjoint from the set of moves that could be played in a single move turn. If none of the moves in the first set can be followed by a second legal move, and the second set is empty, the game ends in stalemate.

When you ask above, "what if the first move is one that would normally prohibit a second move, such as a check, a promotion, a capture, or a double Pawn move subject to en passant?" you are asking about a possible single move turn. It is not stalemate if any such move is available.

I am trying to be succinct, and yet it seems I need to provide more detail here.

2 Move Chess?

This is a fair point. I am open to suggestions on the name. Initially I wanted to use the name "Double Move Chess" and was quite disappointed to find that the name was taken. I clearly failed to do another search, as I was unaware of "Chess2 - The Sequel" until now.

I like "Chess2" because of the double meaning of it being the second version of the game as well as it being characterized by two-move turns. The alternative "Chess2.0" would sort of lose the second meaning.

But you're right, this needs a new name. I will try to think of a better name, and again, suggestions are welcomed!

Thanks.

(Note: my answer below is not clear and not quite correct. It is also out of date--the rules have been renumbered and it should now refer to rule #2. Please disregard this answer and see the full rules and subsequent discussion above.)

Okay, I see that I need to clarify this rule. To answer each of your scenarios:

1. By rule #1, each move of a two-move turn must be individually legal for the position on the board at that moment--it does not matter whether a second move could remove any checks caused by the first move. So if there is no legal first move, it is stalemate.
2. This is stalemate.
3. This is also stalemate.

Would this wording be more clear?

The game ends in stalemate if at the start of his turn a player is not in check and cannot complete either a legal two move turn or a legal single move turn.

The game ends in stalemate if at the start of his turn a player is not in check and has no available legal two move turns and no available legal single move turns.

I'm not sure how to interpret the part I put in boldface. Which of these do you mean?

1. If a legal first move is not available, but a second move could remove any checks caused by the first move, it is not stalemate.

2. If there is a legal first move, but it cannot be followed by a legal second move, it is stalemate.

3. If a player cannot make a legal first move, it is stalemate.

I think it's a bit too late to start using the name Chess2. There are already numerous Chess variants, and you wouldn't be the first or even second person to use the name. Pritchard mentions a Chess Too and a couple Chess IIs, and there is a commercial game described on this site that was called Chess 2 - The Sequel.

This submission is now ready for review. Thanks!

It looks like the ZRF got the King's movement wrong. According to this archived page on the King, the King moves the same as it does in Chess on the Dot, which gives it only six moves near the pole, and it can castle.

I have been testing the ZRF, which I got on the Zillions-of-Games website here:

https://zillions-of-games.com/cgi-bin/zilligames/submissions.cgi?do=show;id=450

It looks like the following may be true:

• The Rook moves as it does in other spherical variants, such as Miller's, Nadvorney's, and Chou's Chess on the Dot.
• The Knight moves as it does in Nadvorney's Spherical Chess, which is the same as it moves in Chess on the Dot.
• The Bishop moves as it does in Chao's Chess on the Dot, though there are some details I'm not sure about yet.
• The Queen moves as a Rook or a Bishop.
• In addition to moving one space as a Queen, a King near a pole can make two moves that are unavailable to Rooks, Bishops, and Queens. It can move to the space on either side of the one directly opposite it across the pole.
• There is no castling.

Thanks, I have corrected the Princess' moveset diagram by adding sideways moves.

The Princess' diagram disagrees with the text in omitting sideways moves

Hi Fergus,

I have elaborated more on the Flying General move and included Janggi as well in the explanation.

What's the Flying General in Xiangqi?

All I did to the original diagram was change its formatting to make it easier to read. I got the idea for putting a box around the main board from Pritchard, who did the same, but unlike him, I left all the inner coordinates in.

While on its own the original diagram on this page was a bit obscure, in conjunction with Fergus' circular diagrams it really clarifies the rationale behind Nadvorney's interpretation of the diagonal move; a bit of thought also reveals why Miller's reasoning in keeping the bishop on its own colour is flawed: if the bishop stays on its own colour you would expect a rook stepping over the pole to change colour as it does on a normal square‐cell board, whereas here (or on any spherical/Klein‐bottle‐shaped board with a multiple of four files) it doesn't. On e.g. a 10‐file board, Miller's reasoning would line up with Nadvorney's.

As for Chess on the Dot, the change in the diagonal's handedness at the poles also keeps it on one colour (on a board of this parity), but isn't stirctly necessary for a closed loop: Nadvorney's version (as can be seen on its diagram) does it just as well, and even Miller's manages, albeit via a much more circuitous route.

Fwiw, here's the original diagram as salvaged from the Internet Archive:

c7  d7  e7  f7  g7  h7  a7  b7  c7  d7  e7  f7
c8  d8  e8  f8  g8  h8  a8  b8  c8  d8  e8  f8
g8  h8  a8  b8  c8  d8  e8  f8  g8  h8  a8  b8
g7  h7  a7  b7  c7  d7  e7  f7  g7  h7  a7  b7
g6  h6  a6  b6  c6  d6  e6  f6  g6  h6  a6  b6
g5  h5  a5  b5  c5  d5  e5  f5  g5  h5  a5  b5
g4  h4  a4  b4  c4  d4  e4  f4  g4  h4  a4  b4
g3  h3  a3  b3  c3  d3  e3  f3  g3  h3  a3  b3
g2  h2  a2  b2  c2  d2  e2  f2  g2  h2  a2  b2
g1  h1  a1  b1  c1  d1  e1  f1  g1  h1  a1  b1
c1  d1  e1  f1  g1  h1  a1  b1  c1  d1  e1  f1
c2  d2  e2  f2  g2  h2  a2  b2  c2  d2  e2  f2 

I have a better idea of how this works now. I was describing a torus in my last comment. Unlike a torus, the north and south poles are not adjacent on a sphere. I will write up a better description and provide some more visual diagrams when I have the time.

The description of this game is very confusing. The middle eight rows make sense. These include a regular Chess board with two files from the other side on each side. This much is like Cylindrical Chess.

g8  h8  a8  b8  c8  d8  e8  f8  g8  h8  a8  b8
g7  h7  a7  b7  c7  d7  e7  f7  g7  h7  a7  b7
g6  h6  a6  b6  c6  d6  e6  f6  g6  h6  a6  b6
g5  h5  a5  b5  c5  d5  e5  f5  g5  h5  a5  b5
g4  h4  a4  b4  c4  d4  e4  f4  g4  h4  a4  b4
g3  h3  a3  b3  c3  d3  e3  f3  g3  h3  a3  b3
g2  h2  a2  b2  c2  d2  e2  f2  g2  h2  a2  b2
g1  h1  a1  b1  c1  d1  e1  f1  g1  h1  a1  b1

But the two rows at the top and bottom do not fit the same pattern. Here is the pattern that would make sense to me:

g2  h2  a2  b2  c2  d2  e2  f2  g2  h2  a2  b2
g1  h1  a1  b1  c1  d1  e1  f1  g1  h1  a1  b1
g8  h8  a8  b8  c8  d8  e8  f8  g8  h8  a8  b8
g7  h7  a7  b7  c7  d7  e7  f7  g7  h7  a7  b7
g6  h6  a6  b6  c6  d6  e6  f6  g6  h6  a6  b6
g5  h5  a5  b5  c5  d5  e5  f5  g5  h5  a5  b5
g4  h4  a4  b4  c4  d4  e4  f4  g4  h4  a4  b4
g3  h3  a3  b3  c3  d3  e3  f3  g3  h3  a3  b3
g2  h2  a2  b2  c2  d2  e2  f2  g2  h2  a2  b2
g1  h1  a1  b1  c1  d1  e1  f1  g1  h1  a1  b1
g8  h8  a8  b8  c8  d8  e8  f8  g8  h8  a8  b8
g7  h7  a7  b7  c7  d7  e7  f7  g7  h7  a7  b7

I do not understand why the pattern on the page is not this.

The reason people are calling it a 'Klein bottle' rather than a sphere is because of the weird situation around the poles.

If you draw the eight spaces surrounding each pole as triangles, then the rook shouldn't pass -- it only crosses edges. If you draw them as squares and try to connect opposites, each pole becomes a 'cross-cap' rather than a point. A sphere with two cross-caps is topologically equivalent to a Klein bottle.

(Alternatively each pole could be a double-handle, then you have an orientable surface of genus 4.)