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Help for TwixT

Introduction

Welcome to the network Twixt server. On a 24x24 board, players take turns placing pegs of their color on the board. Any time a peg is placed a "knight's move" from another peg of the same color, a strut may be placed, connecting them. A strut can not cross over (through) another strut. The object is to connect your (opposite) sides of the board while preventing your opponent from connecting his/her pair of sides.

twixt challenge red-userid black-userid [ -size=#size ] [ -handicap=#handicap ]
Start a new game. The Red player starts and plays vertically. Default board size is 24x24. If a positive handicap is specified, the board's width is reduced by the specified number of columns, therefore making it easier for Black to win (in theory). A positive handicap of only 1 row might just balance out Red's first move advantage. If a negative handicap is given, the board's height is reduced by that many rows, making it easier for Red to win.
 
twixt move board userid password move[#moveno]
Make a move on the specified board (if it is your turn).

Usually, a move is of the form letter a-x or A-X number 1-24, such as j12 or K5, telling where to place a peg. Any links that this peg can make, without removing other links, will automatically be made.

Each time a move is made, both players receive the updated move list and board position. The size of the display you receive is set by using the "small", "medium", "big", or "large" command. (See above.) If you have not sent one of these commands, you will receive the medium display.

UNLINKING AND/OR MANUALLY LINKING

If on your move you wish to remove some of your links, and/or control which links get placed on the board, here's the syntax to follow. Note that the [] symbols mean "what is enclosed is optional."

***NOTE! There should be NO SPACES ANYWHERE in your move.

Each move should conform to the following syntax:

coordinates [ - unlink list ] [ + link list ]

where coordinates = letter a-x or A-X number 1-24

and both types of list are of the form:

coordinates / coordinates [ / coordinates ... ] [ , list ]

Each group of coordinates indicates a "chain" of pegs to link or unlink. Commas are used as delimiters between each chain.

Here's an example of a move using the unlink/link feature.

Before move:
          H  I  J  K  L  M  N  O  P
       10 .  .  .  O_ .  .  #_ .  .     (Only part of the board
                     ---_  /  ---_       is shown here.)
       11 #  .  . _#_ #  O |.  #  #
              _---   ---_ /   /
       12 .  #  . _O_ #_ #  # |.  O
              _---   ---_--_ /   /          # to move.
       13 #  O  .  .  .  O_ #  . |.
                           ---_ /
       14 .  .  .  .  .  .  .  O  .

# makes the move: j12-i12/k11/m12/n10,o11/n13+h11/j12/l11/n12/p11

After move:
          H  I  J  K  L  M  N  O  P
       10 .  .  .  O_ .  .  #_ .  .
                     ---_     ---_
       11 #_ .  .  # _#_ O  .  # _#
            ---_ _---   ---_ _---
       12 .  #  # _O_ #_ #  #  .  O
              _---   ---_--_     /          O to move.
       13 #  O  .  .  .  O_ #  . |.
                           ---_ /
       14 .  .  .  .  .  .  .  O  .

If you provide an unlink list with your move but no link list, the server will first do the unlinks, and then will automatically link all possible links to the peg you just played. The + symbol has the effect of disabling this autolinking feature. Note that in the above example, the link h13/j12 was not made. If for some reason you wish to make no links at all, even though you could link to the peg just played, use the + with nothing after it.

If you should make a mistake in your move that the server recognizes, such as coordinates off the board, impossible to link, impossible to unlink, etc. then nothing will happen on the board. The server will send back a (hopefully informative) error message, and it will still be your move.

If your move completes an uninterrupted chain connecting your border rows, the server will announce that you have won the game.

twixt move board userid password swap
or
twixt swap board userid password
Swap sides in the game. This ONLY works on the second player's (Black's) first move in a non-handicapped game. If you use it, then you will be Red, the peg your opponent just placed will be your peg, and it will be your opponent's move.

This option is included in an attempt to reduce Red's natural first-move advantage. The idea is for Red to make a first move which is not ideal, producing a position with even chances for both sides. Both players should agree to have this option available BEFORE the game begins, of course!

When sides are swapped, the updated move list (with the player's names switched around) and board position will be sent to both players.

TwixT Rules

Twixt is a board game for 2 players, invented by Alex Randolph. It was once marketed in the U.S. by 3M and then Avalon Hill, but now the only distributors of new sets are (I believe) Klee and Schmidt in Europe. You may be able to buy a used set from some mail-order distributors, or if you're lucky, find one in a well-stocked game store. The newsgroup rec.games.board.marketplace may occasionally hold an auction for a used set. Also, http://www.ebay.com frequently holds auctions for used sets. Avalon Hill will be selling new sets again in 1999. If you feel ambitious, you could do like I did, and make your own set. Email me at chmeee@hotmail.com if you would like more details. Anyway, here are the rules to the game, as well as some general comments and a sample game on a small board.

The board is a 24x24 square grid of holes, minus the corner holes. The holes along the edges are referred to as border rows. The "top" and "bottom" border rows are the Red border rows; the "left" and "right" border rows are the Black border rows. (European sets may use different colors.)

Each player has a collection of pegs and links of his/her color. 50 of each (a total of 200 pieces) is an ample supply.

Red moves first, and tries to "build a bridge" connecting top & bottom. Black tries to build a bridge connecting left and right. Since each link is an un-crossable barrier to either side. It is impossible for both sides to have a completed bridge. At the start, the board is empty. A move consists of two parts:

  1. Place one of your color pegs in any empty hole EXCEPT in your opponent's border rows. (This is why there are no corner holes.)
  2. Link any pair or pairs of your pegs that you wish to link. A link may be played ONLY if your two pegs are at opposite corners of a 6-holed rectangle (like a knight's move in chess) and there is no other link blocking your way. Note that your own links will block you as well.

You ARE allowed to remove as many of your OWN links as you wish on your move, prior to placing any. Usually, there is no need to, but you sometimes need the elbow room. (See example B below.) You might conceivably also need to remove some links because you're running out of them. You are also allowed to remove as many of your own pegs as you wish on your move. With at least 40 pegs and 40 links for each side, however, running out of either is extremely unlikely.

(See the twixt special commands for an explanation of move syntax on the server. The server does support link removal, and controlling how you make your links if any. Peg removal is not supported; electronically generated pegs are not about to run out, and there is never any advantage in removing them.)

After Red makes the very first move in an EVEN game, Black has the option of swapping sides if desired. The Red peg would remain on the board, and play continues from this position, with Black making the next move. This 'swap' option is included to reduce the natural advantage of the first move, making the game more evenly balanced.

THE OBJECT is to build an UNINTERRUPTED chain of linked pegs connecting a peg in one of your border rows with a peg in your other border row. If neither side can complete such a chain, the game is a draw.

Draws can occur when one player has an impenetrable barrier to the other, but this barrier is not an uninterrupted chain of linked pegs. For example:


Example A

   E  F  G  H  I  J  K  L

 6 .  .  #_ .  O  #_ .  .         Only part of the board is shown here.
          \---_ \  \---_
 7 .  .  .| .  #| .| .  #         O's border rows are 1 and 24.
           \     \  \  /
 8 .  .  .  #  .  O  # |.         O's I6-J8-K10 chain is connected to the
             \     \  /           top, and J9-K11-J13 is connected to the
 9 .  .  .  .| .  O| #  .         bottom. #'s pegs and links prevent
              \    \\ \           O from connecting these 2 groups.
10 .  .  .  .  #  .| O| .
                \   \  \          Draw.
11 .  .  .  .  .| .  O  #
                 \  /  /
12 .  .  .  .  . _# |. |.
             _---  /  /
13 .  .  .  #  .  O  #  .

Example B

   E  F  G  H  I  J  K  L

 6 .  .  #_ .  O  #_ .  .
          \---_ \  \---_
 7 .  .  .| .  #| .| .  #         O to move.
           \     \  \  /
 8 .  .  .  #  .  O  # |.         Here O can remove the J9-K11 link, and
             \     \  /           then play a peg at I11,
 9 .  .  .  .| .  O| #  .         double-linking to K10 and J13.
              \    \\ \
10 .  .  .  .  #  .| O| .
                    \  \          If O could not remove his link, this
11 .  .  .  #  .  .  O  #         would also be a draw.
             \      /  /
12 .  .  .  .| .  . |. |.
              \    /  /
13 .  .  .  .  #  O  #  .

Here's a sample "game" I made up on a 12x12 TwixT board. For this game, the 'swap' option was NOT allowed.


                       RED

        A   B   C   D   E   F   G   H   I   J   K   L
    1       .   .   .   .   .   .   .   .   .   .

    2   .   R8  .   .   .   .   .   .   .   .   .   .
             \
    3   .   . \ B7  .   .   .   .   .   .   .   .   .
               \ ~~---__
    4   .   .   R3  .   B6  .   B2  .   .   .   .   .
B                \               \                          B
L   5   .   .   . \ .   .   .   . \ .   .   .   .   .       L
A                  \               \                        A
C   6   .   .   .   R7  .   .   R1  B5  .   .   .   .       C
K                  /      _---~/   /                        K
    7   .   .   . / .   R4  . / . / .   .   .   .   .
                 /_---~~     /   /
    8   .   B3  R2  .   .   R6  B1  .   .   .   .   .
             ~~---__         \
    9   .   .   .   B4  .   . \ .   .   .   .   .   .
                               \
   10   .   .   .   .   .   .   R5  .   .   .   .   .

   11   .   .   .   .   .   .   .   .   .   .   .   .

   12       .   .   .   .   .   .   .   .   .   .

                       RED

   RED  BLACK
1.  G6           A solid opening move. By playing midway between the Red
               borders, Red is making Black's task as difficult as possible.
2.       G8      On a larger board, this might be too close to the Red peg,
               but Black's game is already desperate. Black might have tried
               G10 instead, after which 2.E9,G4;3.E5(linking G6),D9;
               4.C8(linking E9),E11(G10,D9);5.B10(C8),D3;6.D2 (Red wins) is
               one possible continuation.
3.  C8           Red gets in Black's way. Playing 4 holes away from your
               opponent's peg like this is frequently a good blocking move
               to make, particularly when the move is supported by a nearby
               peg as it is here.
4.       G4      Black follows the opening maxim: "Don't start a fist fight
               too soon." Simply playing E7 loses to 3.D6(C8),D5(E7);
               4.C4(D6) and Red will win the race to the wall. Note that
               in this variation, Red's G6 peg is not part of the final
               bridge. It's perfectly okay to abandon pegs this way.
                 Black might have played F4, after which one continuation is
               3.E5(G6),D5(F4);4.C6(E5) and Red is unstoppable.
5.  C4           The C4-C8 pegs form what is called a "setup," which means
               they threaten to link together in one move in two different
               ways. C4-G6 also threatens to link in one move, but they can
               only link via E5, so this is not a setup.
6.       B8      Black tries to make two threats at once. Now we're in the
               middle game (things move along quickly on a quarter board.)
7.  E7           (linking G6,C8): the best move. Red covers both threats at
               once. If for example Red had played D6(C4,C8) then
               4. ... D9(B8);5.G10,E7(G8,D9);6.H8(G6,G10),F6(G4,G8) and Black
               has a win. Or if 4.E9(C8),D7(B8);5.E7(C8,G6),F6(G4,D7).
8.       D9      (linking B8): the only move, not that it matters.
9.  G10          Now it's Red's turn to make two threats at once.
10.      H6      (link G4,G8)  Black is just going through the motions.
11. F8           (link G10,G6) E9 was also possible.
12.      E4
13. D6(C4,C8),C3(E4);
14.      B2(C4)  Black resigns.

Here are some pithy aphorisms about the game:

  • Sometimes the best offense is a good defense. See Red's move #2 above. By falling back to block, Red tries to have a "net" built by the time Black gets there.
  • Always keep the whole board in mind. Don't get drawn into a local battle if a distant move would help your position more. Remember just because you put some pegs down doesn't mean they have to be part of your final bridge.
  • Develop an eye for the "diagonals"- for example in the game above, the line B2-C4-D6... was very important for Red. In a "race" such as in the analysis to Black's 2nd move, being at least on such a crucial diagonal means you will win the race to the wall.

HANDICAPS AND THE 'SWAP' RULE

Let us say that Red (the first player to move) has border rows 1 and 24. As mentioned above, Black has the option of swapping sides after Red's first move. This means that an initial move like L12 for Red would actually be a poor choice, because, Black could simply swap and have a winning position. So, what would be a good first move for Red? There is a general consensus among several strong players that the set of all initial moves which lead to equal chances for both sides lies roughly on an ellipse, symmetric about the center of the board, passing through E12 and L7 or L8. This is offered as a rough guide only; you are encouraged to pursue your own ideas about what a good initial move might be.

If desired, you could play a game without allowing any 'swap.' This would be a handicap game, where one player is giving the other the handicap of the first move. In such a game, the initial move L12 would certainly be a strong move. In fact, if the players are of disparate playing strengths, you may wish to invoke a stronger handicap. One possible way to handicap the game is to reduce the width of the playing field, so that the weaker player has less distance to bridge. With an actual game set, this might be indicated with a rubber band of the right size. A 6-row plus first-move handicap can provide a challenging game between an experienced player and a beginner. It is unclear, however, who would have the advantage if the second player (Black) were given a 1-row handicap. (Perhaps this is an alternate way to balance the game.) If you wish to give a "small" handicap of only 1 or 2 rows, let the weaker player move first as well, to be sure you actually are giving a handicap.

POSTSCRIPT: you might like to check out the Twixt puzzles at:

http://www.gamerz.net/~pbmserv/Twixt/puzzles.html

 

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