Gameplay elements and classification

Games can be characterized by "what the player does". This is often referred to as gameplay. Major key elements identified in this context are tools and rules that define the overall context of game.

Tools

Games are often classified by the components required to play them (e.g. miniatures, a ball, cards, a board and pieces, or a computer). In places where the use of leather is well-established, the ball has been a popular game piece throughout recorded history, resulting in a worldwide popularity of ball games such as rugby, basketball, soccer (football), cricket, tennis, and volleyball. Other tools are more idiosyncratic to a certain region. Many countries in Europe, for instance, have unique standard decks of playing cards. Other games such as chess may be traced primarily through the development and evolution of its game pieces.

Many game tools are tokens, meant to represent other things. A token may be a pawn on a board, play money, or an intangible item such as a point scored.

Games such as hide-and-seek or tag do not use any obvious tool; rather, their interactivity is defined by the environment. Games with the same or similar rules may have different gameplay if the environment is altered. For example, hide-and-seek in a school building differs from the same game in a park; an auto race can be radically different depending on the track or street course, even with the same cars.

Rules and aims

Whereas games are often characterized by their tools, they are often defined by their rules. While rules are subject to variations and changes, enough change in the rules usually results in a "new" game. For instance, baseball can be played with "real" baseballs or with wiffleballs. However, if the players decide to play with only three bases, they are arguably playing a different game. There are exceptions to this in that some games deliberately involve the changing of their own rules, but even then there are often immutable meta-rules.

Rules generally determine the time-keeping system, the rights and responsibilities of the players, and each player's goals. Player rights may include when they may spend resources or move tokens.

The rules of a game are to be distinguished from its aims. For most competitive games, the ultimate ‘aim’ is winning: in this sense, checkmate is the aim of chess. Common win conditions are being first to amass a certain quota of points or tokens (as in Settlers of Catan), having the greatest number of tokens at the end of the game (as in Monopoly), or some relationship of one's game tokens to those of one's opponent (as in chess's checkmate). However, when we talk about the aims of a game, we also refer to intermediate aims: the things that you have to do in order to win the game. For instance, an intermediate aim in football is to score goals, because scoring goals will increase your likelihood to win the game (but isn't alone sufficient to win the game).

Aims are not just a 'special' kind of rules: the difference between the rules of a game and the aims of a game is a fundamental one. This can be seen by considering some examples. The aim of chess is to checkmate, but although it is expected that players will try to checkmate each other, it is not a rule of chess that a player must checkmate the other player whenever he can (as a matter of fact, unskilled players often fail to take the opportunity to do so). Similarly, it is not a rule of football that a player must score a goal if he shoots a penalty (it is only expected, and not required, that he will try). On a general level, the distinction between the rules and the aims of a game can be characterised as follows: an aim identifies a sufficient condition for successful action, whereas the rule identifies a necessary condition for permissible action. While meeting the aims often requires a certain degree of skill and (in some cases) luck, following the rules of a game merely requires knowledge of the rules and some careful attempt to follow them; it rarely (if ever) requires luck or demanding skills.

Skill, strategy, and chance

A game's tools and rules will result in its requiring skill, strategy, luck, or a combination thereof, and are classified accordingly.

Games of skill include games of physical skill, such as wrestling, tug of war, hopscotch, target shooting, and stake, and games of mental skill such as checkers and chess. Games of strategy include checkers, chess, Go, arimaa, and tic-tac-toe, and often require special equipment to play them. Games of chance include gambling games (blackjack, Mahjong, roulette, etc.), as well as snakes and ladders and rock, paper, scissors; most require equipment such as cards or dice. However, most games contain two or all three of these elements. For example, American football and baseball involve both physical skill and strategy while tiddlywinks, poker, and Monopoly combine strategy and chance. Many card and board games combine all three; most trick-taking games involve mental skill, strategy, and an element of chance, as do many strategic board games such as Risk, Settlers of Catan, and Carcassonne.

Single-player games

Most games require multiple players. However, single-player games are unique in respect to the type of challenges a player faces. Unlike a game with multiple players competing with or against each other to reach the game's goal, a one-player game is a battle solely against an element of the environment (an artificial opponent), against one's own skills, against time, or against chance. Playing with a yo-yo or playing tennis against a wall is not generally recognized as playing a game due to the lack of any formidable opposition. Many games described as "single-player" may be termed actually puzzles or recreations.

Multiplayer games

A multiplayer game is a game of several players who may be independent opponents or teams. Games with many independent players are difficult to analyze formally using game theory as the players may form and switch coalitions. The term "game" in this context may mean either a true game played for entertainment, or a competitive activity describable in principle by mathematical game theory.

Game theory

John Nash proved that games with several players have a stable solution provided that coalitions between players are disallowed. Nash won the Nobel prize for economics for this important result which extended von Neumann's theory of zero-sum games. Nash's stable solution is known as the Nash equilibrium.

If cooperation between players is allowed, then the game becomes more complex; many concepts have been developed to analyze such games. While these have had some partial success in the fields of economics, politics and conflict, no good general theory has yet been developed.

In quantum game theory, it has been found that the introduction of quantum information into multiplayer games allows a new type of equilibrium strategy not found in traditional games. The entanglement of players's choices can have the effect of a contract by preventing players from profiting from what is known as betrayal.