Triominoes

Triominoes is a variant of dominoes using triangular tiles published in 1965. A popular version of this game is marketed as Tri-Ominos by the Pressman Toy Corp.

A triomino is in the shape of an equilateral triangle approximately 1 in (2.5 cm) on each side and approximately 0.25 in (6.4 mm) thick. Each point of the triangle has a number (most often from 0 to 5), and each triomino has a unique combination of numbers (with repetition of a number allowed in the combination). With the 6 possible end values commonly seen, and with the additional condition that the 3 numbers do not decrease clockwise, there are 56 unique combinations, and thus the standard triomino set has 56 tiles. Larger sets are possible; including 6 as a possible end number would result in 84 tiles.

Tiles are most often made from a plastic or resin that approximates the feel of stone or ivory, similar to most modern commercial domino sets. Numbers are recessed into the surface and painted black. Some "deluxe" sets include a raised brass tackhead in the center, which assists in mixing up or shuffling tiles, as the tackhead reduces the surface area of the tile contacting the table, so tiles move more freely.

Valid play of a triomino is similar to that of a domino in that the sides contacting each other must have matching numbers; two numbers must match. A side with a 1 and a 2 will often not match the side the player is attempting to match. Points are scored based on the numbers on the tile played, with high scores when special placements are made.

At the start, all of the tiles are placed face down and shuffled. Players randomly draw their starting pieces. The specific number depends upon the number of players: a two-player game uses nine pieces per player to start, a three-four players use seven pieces, and a five-six player use six pieces. One player keeps score for all, using columns for each player and cumulative scores.

The player who draws the largest "triple" (all three numbers the same on the tile), begins the game by placing that tile. He scores 10 points plus the total value of the tile. The exception is that if the player with the highest triple tile held also holds a triple zero (or if the triple zero is the only triple held) and the opponent or opponents hold no triples, then that player plays the triple zero and earns 40 points. If no triple is held the player with the highest single tile value plays it and scores its value without the 10 point bonus. When players hold tiles with the same value the next highest counts and so on until there is a highest value tile.

In turn clockwise, each player places a new tile that lines up with the placed tiles. To place a tile, two of the three numbers must align with the adjacent tile. If the tile is placed such that it would touch two other tiles, then all of the adjacent numbers must match. Where the points of tiles meet the numbers must always be the same; if they are not, someone has been allowed to misplace a tile and the round must be restarted.

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Wikipedia