Dominoes are a game system made up of a set of rectangular tiles (the dominoes), each of which is divided into two squares, or ends. Each end has a value associated with it, represented by a number of spots, ranging from 0 (known as blank), to 6 or 9 (and sometimes higher, but generally always a multiple of three), depending on what set is being referred to.
In a set of dominoes, there is exactly one domino of each possible number pairing, including doubles, dominoes which have the same number at each end. Domino sets are usually referred to by the highest double they contain, most commonly Double-6 or Double-9, which contain 28 and 55 dominoes respectively.
Click here for a list of Icehouse games that make use of dominoes.