TwixT

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A computer-generated image of a game of TwixT, as played on littlegolem.net.

TwixT is a two-player abstract strategy game invented by Alex Randolph. It is a member of the connection game family, along with games such as Hex, Havannah, Y, PÜNCT and *Star.

Twixt is played on board with a 24×24 grid of holes, with the four corners missing. The two players are Red and Black; the topmost and bottommost rows belong to Red, and the leftmost and rightmost rows belong to Black. (Different sets may use different colors.)

[edit] Rules

The players take turns placing pegs of their respective colors on the board, one peg per turn.
A player may not place a peg on the rows which belong to his or her opponent.
Red places the first peg. To counteract first-move advantage, the pie rule is suggested. (This "one-move equalization" was added by Randolph after 3M published his game. It is present in the Schmidt Spiele edition and all later editions.)
After placing a peg, you may link one or more pairs of pegs on the board which are all your own colour. The links can only go between two pegs a knight's move away from each other, and cannot cross another link; they block other links, most importantly the opponent's. You may remove your own links (but not your opponent's) in order to rearrange the sequence of links on the board. (Variant for pencil and paper play: you may cross your own links but not your opponent's. See below.)
The first player to make a continuous chain of linked pieces connecting their two sides wins. If neither side can achieve this, the game is a draw.

3M originally published TwixT as part of its Bookshelf Games line; Avalon Hill took over publication at a later date. TwixT is no longer produced in the United States of America, although Schmidt Spiele produced copies of the game in Germany, and Kosmos published a version of the game in 1998.

[edit] Variants

Perhaps the most popular variant is called Twixt PP where PP means paper and pencil. The rules are almost identical to standard Twixt. The only difference is with regard to link removal. When you play with paper and pencil, links are never removed (no erasure necessary,) but your own links are allowed to cross each other. This means, for example, that a winning path might loop across itself. Crossed links are not inherently connected to each other. In other words, the object is still to form a sequence of pegs of your color, each directly linked to the next, which connects your border rows.

In terms of game outcome, for the vast majority of games, this rules change makes no difference. On the Little Golem turn-based server, thousands of games have been played, all using the PP ruleset. Of those, only a handful—less than 0.1%—can be pointed to as reasonably clear examples of games that probably would have ended differently under standard rules. Most of those are games which would have been a draw under standard rules instead of a win for one side. But one game almost certainly would have been a win for one side instead of the other.

A contrived example of such a situation on a smaller board is illustrated at the left. Under PP rules, black to move has an easy win with F9, linking to both E11 and H8. But under standard rules, black would have to first remove the F8/G10 link in order to place F9/H8, and that would allow white to then play at E9, double linking to D11 and G8. White is also threatening to play either i9, which is a triple link, or H10, which is unstoppably connected to the bottom. There is no way for black to effectively block all these threats.

Some players might argue that PP rules are cleaner than standard rules: for one thing, the incidence of draws is reduced. But draws are already quite rare under standard rules, and others believe the extra complications that result from link removal add depth and beauty to the game. In the Randolph series of puzzles, link removal is an essential part of several of those puzzles, and they would not be particularly interesting or challenging positions under PP rules.

Row handicapping is another variant which offers a way for players of different strengths to both enjoy a challenging game together. The simplest handicap is to eliminate the pie rule. Beyond that, one dimension of the grid is reduced. The weaker player moves first and also has less distance to cross. On a physical board, this might be implemented with two extra pieces of neutral color which look nothing like pegs but which fit in the holes. These are placed in the two new corners of the board, which are out of play, to indicate the new location of one of the weaker player's border rows. Six rows plus move might be a reasonable handicap between an experienced player and a beginner. The idea is to find a handicap where each player wins about half the time. Of course there is no pie rule for any handicap game.

Different size grids from the standard 24×24 could be regarded as variants. The 12×12 board shown here leads to a very short game. It might be useful for development of computer programs which play the game, but between humans it is not very interesting. Even on the 24×24 grid, tactical considerations tend to predominate. The opening phase is over quickly, and the rest of the game is spent attempting to tactically justify the plan which you are now stuck with. By comparison, Hex, which has a very similar game object, may have more monotonous tactics, but strategical considerations are much more important. In this sense, Hex is more like Go than Twixt is, since a single move is generally less committal, and mistakes may not be punished as quickly. In my opinion, a larger grid for Twixt would result in greater balance between tactics and strategy. Since most commercial sets use boards which are made from four "quadrants" which either clip together or are hinged, a 36×36 grid could be cobbled together from three sets of the same size. In Europe, there briefly appeared a Twixt knock-off called "Imuri" which used a 30×30 grid. The board had no holes, and lines were drawn to indicate where the links could be placed. But the manufacturing quality was not so great; for example, link paths were drawn at each corner between adjacent border rows (A2 to C1 etc.) This edition was removed from shelves after Mr. Randolph threatened suit.

Mark Thompson's variant Diagonal Twixt has the same rules as standard Twixt, but the border lines no longer run parallel to the square grid of holes. Mark's idea was for border lines which run at a 45 degree angle to the grid ([1]). David Bush's version has the border lines running parallel to link paths. These variants result in many different tactical patterns. They feel like completely new games in this respect.