A domino is a small rectangular block marked with two groups of spots on one side and blank or identically patterned on the other. A domino is used for playing several games, the most popular of which involve a chain reaction. The earliest mention of a domino-like game is found in a document from the Song dynasty, and the modern game appeared in Europe in the 18th century. Dominoes are also popular as pieces of art, and artists construct curved lines, grids that form pictures when they fall, stacked walls and even 3D structures like pyramids. A skillful builder can set up hundreds or thousands of dominoes in a carefully-planned sequence, all toppling with the slightest nudge of just one. The same type of effect is seen in domino shows, where domino builders compete to see who can build the most complex and imaginative domino effects or reactions before a live audience.

The most common domino sets contain 28 tiles and are called double six or double nine. Larger sets exist, but these are not commonly used. The number of pips on each end is the key to determining whether a domino counts for points or not. A domino scores points when its total is exactly divisible by five or three, so that all matching ends have the same number. Each player has a hand of dominoes and plays a domino by placing it on the table positioned so that it touches an end of another domino. This ends up forming a line of matching dominoes which grows in length as the play continues. When a player has reached the set point, which is usually 61, the round ends and the winning player scores points.

Most domino games are based on blocking, or the ability to prevent an opponent from emptying his or her hand by occupying spaces in a line. The first player to do so wins the hand. In team play, the winning team is the one that has a minimum of four legal dominoes in its line.

There are several types of domino games, but they all fall into two categories: blocking games and scoring games. In blocking games, the objective is to get rid of your own dominoes before the other players have a chance to do so. In scoring games, the goal is to get as many points as possible by completing a chain of dominoes that has all of its ends showing matching numbers.

Physicist Stephen Morris, who studies the dynamics of dominoes and their effects on the world around them, explains that a domino that is standing upright has potential energy, which is stored based on its position. When the first domino is pushed over, much of this potential energy is converted into kinetic energy causing the domino to fall and begin a chain reaction.

The same principle applies to story writing. If a writer is a pantster, or doesn’t make detailed outlines of plot ahead of time, the scenes that he or she writes may not have a clear connection to those that come before them or impact on those that follow. This leads to scenes that are either too far back or have little logical impact on the scene that precedes them, like a domino that isn’t tipped just so.