Domino is a game in which players take turns placing domino tiles on the table, positioning them so that each has an open end facing another. The result is a long chain of dominoes. The way that these chains develop provides much of the entertainment in the game. The tiles may be joined together in two ways: 1) the line of play is lengthwise, the dominoes played end to end; or 2) they are joined across the line of play, the dominoes being placed so that each tile touches a matching number on another tile.
Each domino has a square surface and is marked with a sequence of dots called pips, usually in a single color (usually black or white). These pips show the value of each side of the domino, from its greatest value at one end to none at all at the other end. The values of the two ends are also known as the rank and weight of a domino. A domino with a larger number of pips is said to be “heavier” than a domino with fewer or no pips.
The most common domino sets have a maximum of four pips on each end. This is insufficient for many games, so some sets are extended by adding additional pips on the existing ends. The most common extensions are double-six, double-nine and double-twelve. These extend the total number of available dominoes by three, and allow more than four players to play.
As the popularity of domino increased, new rules and variations on the basic game developed. Some of these were designed to provide an element of skill, while others were intended to make the game easier and faster to play. In the latter case, the speed of play tended to increase the risk of making mistakes, which would require more work to correct.
Some domino games are positional; in such games each player lays a tile edge to edge against an already-set tile. The player to his left then adds a tile, either by placing it on the edge of the existing tile or by placing it in the gap between two adjacent dominoes. The next player then takes his turn, and so on until the entire line of play is completed.
There are some situations in which no one is able to make another play and the game is blocked, or deadlocked. This can occur when all the tiles are drawn and no player has a domino in his hand that matches a piece in the line of play.
Other situations in which the game can be blocked are when a player has more than the minimum number of tiles allowed for his turn, or when the dominoes in a player’s hand are unable to form a match with any of the other players’ hands. When this happens, the player must draw extra tiles from the stock, which are then reshuffled before each player draws again.