A single-player video game is a variant of a particular video game where input from only one player is expected throughout the course of the gaming session. "Single-player game" usually implies a game that can only be played by one person, while "single-player mode" usually refers to an option in a normally one player game where more than 1 player play may be also played in a different mode. The majority of early computer games were single-player. Two-player games appeared with the first personal computers, and 1978 introduced the first multiplayer games, known as MUDs. The early 1990s introduced many games which utilized local area networks and null modems for multiplayer mode. Doom is a notable example of one such game.
The major selling points of larger single-player games are interesting storylines, impressive graphics, and realistic non-player characters and opponents. Notable examples include the Half-Life, Doom and The Legend of Zelda series. Selling points of the smaller games are low learning curve and availability (many are free to play on various sites).
Certain game genres are inherently oriented towards single-player in their design. Such genres include puzzle games, such as Tetris, and plot-based role-playing games (RPGs). Recent additions to these genres, such as the MMOGs or online multiplayer versions of Tetris are serving to undo this trend.
The vast majority of modern console games and arcade games are designed so that they can be played by a single player; although many of these games have modes that allow two or more players to play (not necessarily simultaneously), very few actually require more than one player for the game to be played. The Unreal Tournament series is an example of such.