Connection Games Codexery

TwixT

A connection game of pegs and links on a pegboard.

TwixT

TwixT is a two-player strategy board game from the 1960s, part of the early 3M bookshelf game line. It became one of the most popular and long-lasting titles in that series. The game is a connection game: players take turns placing pegs and links on a pegboard, trying to connect their opposite sides.

The game was invented as a paper-and-pencil game in 1957 by designer Alex Randolph. In 1961, when Randolph and Sid Sackson were hired by 3M to start a games division, TwixT was released as a board game—one of the first in the 3M bookshelf series. Avalon Hill took over publication in 1976 after 3M sold its game division. Hasbro acquired Avalon Hill’s parent company in 1998, and the game was discontinued. It is no longer produced in the United States, but a series of German companies have manufactured it under license from Avalon since the 1970s. TwixT was shortlisted for the first Spiel des Jahres award in 1979 and was inducted into the Academy of Adventure Gaming Arts & Design’s Hall of Fame, alongside Randolph, in 2011.

The board is a 24×24 grid of holes, minus the four corner holes. Pieces include pegs, which fit into the holes, and links, which fit into the tops of pegs to connect them. In the 3M edition, players are Red and Black; other editions may use different colors. The top and bottom rows belong to the lighter color; the left and right rows to the darker color. Players alternate placing one peg per turn, with the lighter color moving first. A peg cannot be placed on an opponent’s border rows. To counter first-move advantage, the pie rule is suggested: after the first peg is placed, the second player may swap sides. If the second player does not swap immediately, sides cannot be swapped later. Randolph added this rule after 3M published the game; it appears in the Schmidt Spiele edition and all later editions.

After placing a peg, a player may link one or more pairs of their own pegs. Links can only connect pegs that are a knight’s move apart, and they cannot cross another link—they block other links, especially the opponent’s. A player may remove their own links (but not the opponent’s) to rearrange them. A pencil-and-paper variant allows a player’s links to cross each other. The goal is to form a continuous chain of linked pegs connecting the player’s border rows. If neither player can do this, the game is a draw.

For general rectangular boards, T

complexity_proven
PSPACE-complete

Lore & Background

TwixT was invented as a paper and pencil game in 1957 by Alex Randolph. When Alex was commissioned along with Sid Sackson by 3M in 1961 to start a games division, the game was issued as a boardgame, one of the first 3M bookshelf games. Avalon Hill took over publication in 1976 when 3M sold its game division. Avalon's parent company was acquired by Hasbro in 1998, and the game was discontinued. The game is no longer produced in the United States, but a succession of German companies has produced the game since the 1970s under license from Avalon. TwixT was short-listed for the first Spiel des Jahres in 1979, and was inducted into the Academy of Adventure Gaming Arts & Design's Hall of Fame, along with Randolph, in 2011.

Reader's Guide

TwixT is played on a board comprising a 24×24 square grid of holes (minus 4 corner holes). Players take turns placing pegs of their respective colors, then may link pegs a knight's move apart. The object is to make a continuous chain of linked pegs connecting the player's border rows. The pie rule is suggested to counteract first-move advantage. TwixT has been proven PSPACE-complete for determining the game value, via a reduction from Hex, and NP-complete regarding whether a single set of vertices can support a connecting path, via a reduction from 3-satisfiability. These proofs indicate a complex strategy; the game has not been solved, no winning strategy has been discovered, nor is the outcome of the game with perfect play known. The official world championships were held as part of the Mind Sports Olympiad in 1997, 1998 and 1999, and again from 2011 to 2022. Games magazine included TwixT in their 'Top 100 Games' for 1980, 1981, and 1982.

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