Toutenkou
Toutenkou 「東天紅」 is a special 3-player mahjong variation mainly popular in Kanto region. Currently available in Tenhou computer matches.
Rule Introduction
Only uses 
of manzu tiles, while all of pinzu, souzu and honor tiles are used (including red fives 
). 112 tiles in total.
are gari 「ガリ」 (similar to nukidora). 20 rinshan tiles in total.
A valid winning hand must include at least one of any regular yakus (identical to regular riichi mahjong yakus). A hand cannot win with only special yakus.
Instead of calculating with fu and han, the score is only counted with points.
Ron takes points from only one opponent (with 8 more extra points than tsumo).
Tsumo takes points from two opponents.
Special Yakus
(1 pt) Oya 「親」: Add one point when winning as dealer.
(1 pt) Menzen 「門前」: Add one point when the winning hand is concealed.
(1 pt) Honba 「本場」: Add one point for each honba.
(1 pt) Gari 「ガリ」: Add one point for each nukidora (). For it is also a red dora, so it actually worths 2 points.
(2 pts) Base point 「バンバン」: Add two points for each winning hand for no reason.
(2 pts) Minkan 「明槓」: Add two points for each opened kan.
(4 pts) Ankan 「暗槓」: Add four points for each concealed kan.
(4 pts) Set 「セット」: Add four points for each collected set of gari (four identical tiles of gari). Can be stacked with gari.
(8 pts) Ron 「ロン」: Add eight points when winning by other's dealing-in.
(10 / 20 pts) Crow 「カラス」: Winning a hand without drawing any gari tiles. Add 10 points when winning hand is opened, while 20 points when concealed.
(20 pts) All Gari 「全ガリ」: Add twenty points when collecting all gari tiles. Can be stacked with gari.
References
External Links
- Toutenkou in Japanese Wikipedia