How to play Mahjong

Mahjong

The four-player tile game, under the Chinese Official rules the World Mahjong Organisation publishes. You build a hand of fourteen tiles out of four sets and a pair, taking one tile at a time and throwing one away, and you may take the tile somebody else throws if it finishes a set. The catch, and the whole game, is that a hand has to be worth eight points before you are allowed to win with it.

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The tiles and the deal

A hundred and forty-four tiles: thirty-four kinds with four of every kind, and eight flowers, one of each.
Three suits run one to nine. Characters, dots and bamboo. A one and a nine are terminals and the rest are simples.
The honours are the four winds, east, south, west and north, and the three dragons, red, green and white. They are in no order and make no runs.
Everybody is dealt thirteen tiles and the dealer fourteen, so the dealer starts by throwing one away.
A flower is not part of a hand. Whoever draws one lays it face up and draws again from the back of the wall, and it is worth a point at the end.

Your turn

Take a tile from the wall, then throw one away. Your hand is thirteen tiles between turns and fourteen while you are deciding.
Play goes to the right, which is counterclockwise round the table.
A set is three of a kind, a run of three in one suit, or four of a kind. A finished hand is four sets and a pair.
The wall is public. The page shows how many tiles are left in it, and everything anybody has thrown away stays face up in front of them for the rest of the hand.

Claiming what somebody throws

A thrown tile can be taken by anybody it finishes a set for, and taking it ends that player's turn wherever they are sitting.
Three of a kind or four of a kind can be claimed from anybody. A run can only be claimed from the player on your left, the one who would have played before you anyway.
A win beats a claim for a set, and a set beats a run. If two players could win on the same tile it goes to whoever sits nearer after the thrower.
A claimed set is laid face up and stays there. It is still your hand and it still counts, but everybody can see it, and some scoring elements need a hand nobody has seen.
You are only asked when you can actually claim, and you have the same move deadline as any other move. Let the tile go and play carries on as if you had not been asked.

Kongs and flowers

Four of a kind is a kong. Declare it and draw a replacement from the back of the wall, because a kong is worth three tiles towards your hand and you still need fourteen.
A kong made from four tiles in your hand stays face down until the hand ends. One made by claiming, or by adding a fourth tile to a set you have already laid down, is face up.
Adding that fourth tile to a set already on the table is the one moment somebody else can take it: a player who could win on that tile may rob the kong.
A flower drawn at any time is laid down and replaced at once, and the replacement can be a flower too.

Winning a hand

A hand of fourteen tiles wins when it is four sets and a pair, and it must be worth at least eight points not counting flowers. A complete hand worth seven is not a win, and the site will not let you declare it.
Two structures break the four sets and a pair rule: seven pairs, and the thirteen orphans, which is one of each terminal and honour plus a second of any of them.
You can win on a tile you drew, or on one somebody threw, or by robbing a kong.
If the wall runs out before anybody wins, the hand is over and nobody scores.

The points

The hand is scored against the federation's list of eighty-one scoring elements, from one point to eighty-eight, and its score is the best combination of them that the hand actually contains.
A few common ones: all runs is two, a hand nobody has seen is four, all of one suit is twenty-four, and all four winds as sets is the top grade of eighty-eight.
Each element counts once, and elements that are simply part of a bigger one are not counted again beside it.
A win on a tile you drew: each of the other three gives you eight plus the hand's points.
A win on a tile somebody threw: the player who threw it gives you eight plus the points, and the other two give you eight each.
Flowers are a point each and are added after the eight point minimum has been met, so they cannot get a hand over the line.
Points move between the four seats and always add up to zero, so a total can go negative and nothing else changes hands.

How a game ends

A game is four rounds of four hands, sixteen hands, and then it is over whoever is ahead.
The deal passes to the right after every hand whether the dealer won or not, so everybody deals four times and everybody is east four times.
The prevailing wind is east for the first four hands, then south, then west, then north, and it matters because a set of the prevailing wind scores.
The highest total wins. Equal totals share a place, and a shared first is a draw.
Every move has a deadline. A player who runs out of time at a four person table is played by the bot and the game carries on; at a smaller table the game ends.

Worth knowing before you start

Two, three or four people can start a game, and the table is always four hands: the bot fills the empty chairs, and a game with a bot in it is unrated.
The page pauses while a thrown tile is being offered around. It does not say who is thinking about it, and there is nothing on your page that could tell you.
Whether somebody let a tile go is in the game log, which is readable once the game is over and not before.
The wall is dealt from the game's seed, and the seed is published at the end, so anybody can check that the tiles came out as they should have.
If you know another mahjong, three things here will surprise you: a run can only be claimed from your left, a hand has to reach eight points to win at all, and the deal passes every hand.

The rules are the World Mahjong Organisation's Chinese Official rules, and the eighty-one scoring elements on this page are that federation's list rather than a selection of ours. The wall is dealt from the game's seed, which is published when the game ends, so a finished game can be replayed tile by tile and checked. What the site adds is the deadline, the bot in an empty chair, and the refusal to let you declare a win worth fewer than eight points.

Mahjong terms

A chow: A run of three in one suit. Claimable only from the player on your left.
A pung: Three of a kind. Claimable from anybody.
A kong: Four of a kind. Worth three tiles towards your hand, so declaring one earns a replacement draw.
A flower: One of the eight bonus tiles. Not part of a hand: laid down and replaced at once, and a point at the end.
The wall: The tiles nobody has yet. Drawn from at the front, and from the back for replacements. When it runs out the hand ends with nobody winning.
A fan: One of the eighty-one scoring elements. The word is also used for the points themselves.
The prevalent wind: East for the first four hands, then south, west and north. A set of it scores.
The seat wind: Your own wind, which depends on where you sit relative to the dealer. A set of it scores too.
Robbing the kong: Winning on the fourth tile somebody adds to a set already on the table. Worth eight on its own.

Playing it here

Against a person or the bot. The bot needs no account and starts at once. To play a person, be rated and keep your games, you need an account: an email address and a password.
At your own pace. Every move has a deadline you both see, from one minute to a week. A game can take an evening or it can take a fortnight.
Nothing to buy and nothing to win. No stakes, no prizes, no boosts, no undo. The only thing on offer is a place on a leaderboard, and only if you want one.
Every game can be checked. Anything decided by chance comes from the game's seed, and the seed is published the moment the game ends, so any finished game can be replayed and verified by anyone. See fair play.