Four-player Game Mahjong Rules

Each player takes a turn picking up a tile from the wall and then discarding a tile by throwing it into the center and, if desired, announcing out loud what the piece is. Play continues this way until one player has a legal winning hand and calls out Mahjong while revealing their hand. There are 4 different ways that this order of play can be interrupted.
During play, the number of tiles maintained by each player should always be thirteen tiles (meaning in each turn a tile must be picked up and another discarded). Not included in the count of thirteen tiles are Flowers and Seasons set to the side and the 4th added piece of a Kong. If a player is seen to have more or less than thirteen tiles in their hand outside of their turn they are penalised.
Japanese and Korean Mahjong have some special rules. A player cannot win by a discard if that player had already discarded that piece, where players' discards are kept in neat rows in front of them. Players may declare ready, meaning that they need one tile to win, cannot change their hand and win extra points if they win. Some rules may replace some of the number 5 tiles with red tiles, as they can earn more points. Korean Mahjong does not allow melded (stolen) chows. Taiwanese Mahjong adds 3 tiles to a hand requiring a 5th set to be formed, making a clean hand or all Pong hand very difficult to procure. American Mahjong has distinctive game mechanics and the article on American Mahjong details these. Some differences include many special patterns, a different scoring system and the use of jokers and 5 of a kind.
However, many mahjong video games, especially among those released in Western territories, do not depict the actual game of mahjong but rather mahjong solitaire.

Mahjong Solitaire (Mahjong Tower) Rules

Mahjong solitaire is a puzzle game based on the same tiles. The goal is to match open pairs of identical tiles and remove them from the board, exposing the tiles under them for play. The game is finished when all pairs of tiles have been removed from the board or when there are no exposed pairs remaining.
The 144 tiles are arranged in a special four-layer pattern with their faces upwards. A tile is said to be open or exposed if it can be moved either left or right without disturbing other tiles. The goal is to match open pairs of identical tiles and remove them from the board, exposing the tiles under them for play. The game is finished when all pairs of tiles have been removed from the board or when there are no exposed pairs remaining.
Tiles that are below other tiles cannot be seen. But by repeated undos and/or restarts which some programs offer, one gradually gets more and more information. Sometimes, tiles are only partially covered by other tiles, and the extent to which such tiles can be distinguished depends on the actual tile set.

Mahjong Connect (Mahjong Links) Rules

Look for two identical tiles with a clear path between them. There cannot be more than two 90-degree turns between the tiles. Use your mouse to click one tile, then the other, to remove them from the board. Repeat until all tiles are gone.