General Rules & Definitions for the game of XONG™

the leg game of shape and space

Invented by Nathan A. Smith in 1996.
Copyright 1996,2002,2003,2004 Nathan A. Smith

Introduction & Historical Background

Xong™ is a two-player abstract game invented by Nathan A. Smith in 1996, evolved from another game he invented in 1982, QuintHex™. QuintHex™ was the first game to employ the placement of pieces made of hexagon legs to surround hexagons for territory points. It used dual sets of the 12 quintastix, made by joining 5 legs together, one set for each color. It suffered from the most common abstract game problem: the first player has an advantage. A single-legged piece was initially given to the 2nd player to use as an attempt to even up the game. In the usenet group,, often this problem would crop up. Discussion would then frequently veer into such things as Progressive Chess. Progressive Chess is a fairy chess game that addresses this problem by giving each player at turn N a gradually increasing number of simultaneous moves equal to N. Xong took this idea, along with a familiar peculiarity of the sport of Baseball, and thus came into existence as a candidate for a solution of the first player problem. The Baseball peculiarity is the observation that, among the major sporting games, it is the only one to have each play begin with the ball in the hands of the defense. Xong employs the same idea, for without this concept, Xong would not work in bringing out the progressive nature of each move. The pieces used in the game, called Xoids, gradually increase in size to avoid repetition. Because of the finite size set at the beginning of the game, the remaining available space will shrink in an unpredictable way. As this occurs, habitats for certain types of Xoids will disappear. Keeping track of these events is a wise idea in planning ahead. You can see a quick summary of the rules here.

The Complete Rules

1. Xong is played on a two-dimensional tiling grid of a number of hexagons, connected snuggly together along their edges, corner to corner.

The number of hexagons may vary, but it may also be standardized as it is in the case of the Standard Game. The Standard Game has 61 hexagons arranged in a large hexagonal honeycomb, five on a side all around. The number of sides connecting these hexagons is 210, counting the outer sides at the perimeter of the playing surface. In non-standard varieties, the board may be a random generated grid of hexagons ranging from 48 to 80 or so (no real limitation is enforced, only practical considerations determine the lower & upper bounds). It may also be a symmetrical shape of hexagons. It may also be a number of islands of hexagon collections, within reason. The playing surface should be more blob-like than stringy. The possible board shapes fall under a similar category to polyominoes, called hexominoes, but because they are preferred to be blob-like, there are not as many good boards to choose from as there are 61-order hexominoes!!

2. Xoids consist of an integer number of hexagon sides, or legs, joined together in a rigid fashion. When a Xoid is rotated or flipped over, it is the same Xoid. In order to be a new Xoid, it cannot be rotated and/or flipped over into the same shape as any Xoid already placed on the board.

Xoids also fall into a category of collections similar to polyominoes. There is only 1 one-legged piece and only 1 two-legged piece. There are 3 three-legged pieces. There are 4 four-legged pieces and 12 five-legged pieces. There are 27 six-legged pieces. The number rapidly increases from there. If any arbitrary Xoid can be legally placed on the board, it is legal. It does not matter how big it is. It only needs to fit on the board.

3. Each turn consists of two parts. First: placing the given Xoid piece somewhere legally on the board and, Second: whenever possible, giving the other player a new Xoid that legally fits.

The given Xoid may be placed anywhere it fits, taking only vacant legs in the exact same shape as the Xoid. Only one piece may be played on each leg of the playing surface. All legs must fit against at least one hexagon forming the playing surface. You cannot overlap legs occupied from previous play. If there exists any vacant shape in the form of an unplayed Xoid, then, even if that is the only place a new Xoid would fit, you must give the other player a new Xoid. A Xoid is new if it cannot be rotated or flipped over into the same shape as a Xoid already played.

    4. The game ends when no new Xoid can be legally placed on the board. When a player is unable to give the opponent a new Xoid, instead the player gives the opponent 1 point.

    For the Standard Game of 61 hexagons and 210 legs, this occurs around the 31st move of the game, plus or minus 2 or 3, depending on how tightly play has been.

    5. The game begins with the second player giving the first player the first new Xoid.

    For evenly matched games, this first Xoid is usually underwhelmingly the one-legged piece. For handicapped games, a long straight Xoid of N>1 legs is often given. Typically the pieces start out as small as possible, progressively growing in size. During the game, the remaining space available will shrink into strangeness. It is wise to watch how habitat extinction occurs for certain Xoid species and be ready to pounce when the opportunity occurs.

    6. SCORING: At the end of the game, each hexagon in contact with only one player's Xoid legs scores 2 points for that player. In addition, the player NOT LAST to place a Xoid on the board scores 1 point.

    For each hexagon touched first, the player scores 1 point. For each hexagon then cut off from contact by the other player, the player scores 1 point. For each hexagon touched by both players, the first player to touch it loses 1 point and the hexagon is said to be greened out. Finally, when a player is unable to give the other player a new Xoid, then, as a means of compensation, instead 1 point is given to the other player.

    Effectively, this means hexagons are worth 2 points: 1 for touching it first, the other for roping it off from the other player. The last player giving the other player 1 point will eliminate the possibility of a tie game. This wording is to encourage the real-estate gold rush at the outset of the game, avoiding double-touching hexagons or premature perimeter contact.

    An immediate consequence of this scoring is that you can calculate a cold value of any move by counting up how many new hexagons it touches, how many of your opponent hexagons it greens out, and how many of own your hexagons it cashes, and, finally, how many of your opponent hexagons it regrettably cashes. However, to always rely on the best cold value for each move is not a uniformly optimal strategy, and infact can be dangerous.

    A second consequence of the scoring is that you may get a rough standing on the state of affairs of the game by summing up the hexagons that have been touched but not greened out. For each hexagon cashed (roped off from the opponent), count 2. For each hexagon touched but not cashed, count 1.

    7. The player with the most points at the end of the game wins.

    For the Standard Game of 61 hexagons the average score is about 23 to 24 points for each side.

    Quick Rules Summary:

    1. Xong™ is played on a 2-dimensional tiled grid of about 61 connected hexagons.

    2. The playing pieces, called Xoids, are made of an integer number of hexagon sides or legs joined rigidly together. In order to be a new Xoid it cannot be rotated and/or flipped over into the shape of a Xoid already on the board.

    3. Each turn is done in 2 steps: place the given piece, make & give the next new piece.

    4. The game ends when no new Xoid can be legally played on the board.

    5. The game begins with the 2nd player giving the 1st player the 1st Xoid.

    6. At the end of the game:

          each player's hexagons are worth 2 points each
          not being last is worth 1 point

    7. The highest tally of points at the end of the game wins.

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