A game is a structured form of play, usually undertaken for entertainment or fun, and sometimes used as an educational tool. Many games are also considered to be work (such as professional players of spectator sports or games) or art (such as jigsaw puzzles or games involving an artistic layout such as Mahjong, solitaire, or some video games). Games are sometimes played purely for enjoyment, sometimes for achievement or reward as well. They can be played alone, in teams, or online; by amateurs or by professionals.
In tabletop games and video games, game mechanics are the rules or ludemes that govern and guide the player's actions, as well as the game's response to them. A rule is an instruction on how to play, a ludeme is an element of play like the L-shaped move of the knight in chess. A game's mechanics thus effectively specify how the game will work for the people who play it. There are no accepted definitions of game mechanics.
Game design is the process of creating and shaping the mechanics, systems, and rules of a game. Games can be created for entertainment, education, exercise, or experimental purposes. Increasingly, elements and principles of game design are also applied to other interactions, in the form of gamification.
Game balance is a branch of game design with the intention of improving gameplay and user experience by balancing difficulty and fairness. Game balance consists of adjusting rewards, challenges, and/or elements of a game to create the intended player experience. Game balance is generally understood as introducing a level of fairness for the players. This includes adjusting difficulty, win-loss conditions, game states, economy balancing, and so on to work in tandem with each other. The concept of game balance depends on the game genre.
Game theory is the study of mathematical models of strategic interactions among rational agents. It has applications in all fields of social science, as well as in logic, systems science and computer science. The concepts of game theory are used extensively in economics as well. The traditional methods of game theory addressed two-person zero-sum games, in which each participant's gains or losses are exactly balanced by the losses and gains of other participants.