Riichi/Dora Mahjong - Quick Rules
The TilesPlayYaku and Valid HandsEnd of a HandStrategyAdditional ComplexitiesChii ToiFuritenKanDora
The Tiles
A mahjong set consists of tiles numbered one through nine in three suits, four winds, and three dragons (sometimes called colors). There are four copies of each tile.
The suited tiles consist of the characters (or man), each containing a Chinese numeral:
The dots (or pin), each containing a number of colored circles:
And the bamboo (or sou), each containing a number of bamboo bundles. (The one-bamboo tile often contains a bird.)
There is one wind tile each for East (ton), South (nan), West (xia), and North (pei). Each is marked with the Chinese character:
And the three colored tiles Red (chun or aka), White (haku or shiro) and Green (hatsu or ao). The Red and Green tiles are marked with a Chinese character. The White is often blank.
Play
Your tiles are at the bottom. To each player's left is their score and "seat" direction. "Wall" is the number of tiles left to be drawn.
You have thirteen tiles in your hand. On your turn, you draw a fourteenth tile and then click a tile to discard it. The goal is to form your hand into four groups of three plus one pair. (Unlike rummy games, you do not discard after completing your hand.)
A group of three can consist of three sequential tiles of the same suit.
Or three identical tiles. Wind and dragon tiles can only form groups of identical tiles.
An opponent's discard can be taken to complete a group. A tile that completes your hand can be taken from any player. A tile that completes a group of three identical tiles can be taken from any player. A tile that completes a sequence can only be taken from the player at your left (unless it completes your hand). When a tile is taken, the completed group is displayed. After taking a tile, your hand is called exposed.
When you can take a tile, buttons will appear below your hand with the possible groups it could form. A sequence is called Chii. A group of three is called Pon. Winning is called Ron.
Completing your hand with the tile you drew is called tsumo.
Yaku and Valid Hands
In order to win, your hand must contain at least one of the following special configurations (called yaku). The following are the most commonly formed yaku:
Menzen Tsumo
Your hand was completed without taking any tiles from opponent's discards.
Pinfu
Your hand is composed of four sequences, none of which are exposed. The winning tile must be the end tile of one of the sequences.
Tanyao
Your hand contains no winds, dragons, ones or nines.
Fanpai
Your hand contains a group of three dragons, the seat or round wind.
Iipeikou
Your hand contains two identical sequences. No tiles (except for your winning tile) may be taken from discards.
Itsu
Your hand contains three sequences in the same suit running one through nine.
Chanta
All groups in your hand contain a wind, dragon, one, or nine.
San Shoku Dou
Your hand contains three sequences, one in each suit, with the same numbers.
San Ankou
Your hand contains three sets of identical tiles none of which have tiles taken from opponent's discards.
Toi Toi
All groups in your hand a sets of identical tiles.
Hon Itsu
All tiles in your hand, excluding dragons and winds, are of the same suit.
Riichi
If your hand has no exposed groups and (after discarding) you only require one tile to win, you may call riichi. After calling riichi, you may not change your hand. Any tile you cannot win off of must be discarded.
Additional Notes
A hand can contain more than one yaku.
This hand contains Ii Pei Kou (from the two sequences of 1, 2, 3); Fanpai (from the group of red dragons); and Hon Itsu (since the only suited tiles are dots).
End of a Hand
The winning hand is scored based on the number and value of yaku it contains. If the final tile was taken from a discard, that person pays the entire value of the hand. If the final tile was drawn, all opponents pay a portion of the hand's value.
If no player completes their hand before the tiles are exhausted, players are divided into those whose hands are one tile away from completion (tenpai) and those who are not (noten). A penalty is paid by the noten players.
If East won (or was tenpai when no one won), that player remains as East for the next hand. Otherwise, the deal rotates with South becoming East. When the deal rotates for the fourth time, the South round begins. When the deal rotates for the eighth time, the game is over.
Strategy
Taking opponent's discards prevents you from making the Pinfu or Riichi yaku. Since these are the easiest to form, you need to have plan when taking discards.
Not losing is almost as important as winning. Discarding an opponent's winning tile will cost you at least two times (and usually more) than if they won another way. You can guess at what tiles an opponent needs to win by their discards.
Certain arrangements of tiles have multiple ways to win. This hand can with with a 2-dot or 5-dot to complete the sequence. Or it can use the 2-dots as a pair and win off of a red dragon.
Additional Complexities
Chii Toi
A hand consisting of seven unique pairs is also complete and is a yaku.
Furiten
You may not win off of a discard if either:
you have discarded a tile you can win off of.
you have passed on taking a discard you could have won off of since your last turn.
you have passed on taking a discard you could have won off of after declaring riichi.
Kan
When you have four matching tiles in your hand, you may show these tiles as group. This group is treated the same as a group of three when forming a hand.
If you hold three of a tile and the fourth is discarded, it may be taken to form a kan. If you have three of a tile exposed in a group and draw the fourth, it may be added to the group forming a kan. In both of these cases, the kan is exposed.
After forming a kan, a replacement tile is drawn.
Dora
One tile is turned as the dora indicator at the start of a hand. An additional tile is turned over after each Kan.
If the winning player declared riichi, the number of dora indicators is doubled.
The dora are the next tile in sequence. One higher for suited tiles, wrapping from nine to one. The next wind (East, South, West, North, East) for winds. The next dragon (Red, White, Green, Red) or dragons.
Each dora present in the winning hand increases its value.