This ruleset assumes that you have read base.md.
The wall for HKOS consists of the 1-9 character tiles, 1-9 circle tiles, 1-9 bamboo tiles, the four wind tiles, the three dragon tiles, the four flower tiles, and the four season tiles.
To win, you must achieve one of the following:
- Four sets and a pair (as usual)
- One of each terminal/honor tile, plus one extra
- Seven flowers/seasons
In addition, you must have a 3 fan hand minimum in order to win. This is only a problem for four-sets-and-a-pair hands, as the other two conditions automatically give you much more than 3 fan.
At the beginning of each round, you must declare all flowers/seasons in your hand before making any discards. This happens in an initial go-around before the first discard.
A dead wall is sometimes used. The HKOS implementation in Riichi Advanced does not use a dead wall.
For the yaku table and scoring table, consult this guide.