Mahjong
A single-player version of this game exists, called Mahjong Solitaire. It is based on the four-player game, but can be played by one person, so it is one of the games that are played often on computers (such as Solitaire, Spider Solitaire, or Minesweeper). Mahjong Solitaire is much simpler than four-player Mahjong: it is played without dice or chips, by removing tiles (set up in the shape of a pyramid) from the board in sets of two. Each set of two has to match - they are either exactly the same, or go together (two "flowers" tiles, for example). A Mahjong Solitaire player wins when he picks up all the tiles, or he loses when he runs out of sets of two that he can pick up.