Suji: Difference between revisions

*Therefore, if a tile in a suji interval is safe, then other tiles in that interval become safer against that player. For example, if an opponent discards a 4, then the 1 of the same suit is safer. This is because, if they had a wait that wins off the 1-4 interval (such as {23}), then it would be subject to furiten. Similarly, the 7 also becomes safer when a 4 is discarded, due to the 4-7 interval.

Note: suji also applies to the other forms of furiten. After an opponent declares [[riichi]], then any non-winning tile discarded by anyone becomes safe. Therefore, suji can be applied to these tiles as well. If an opponent declares riichi, and the next opponent discards a 4, then 1 and 7 are also considered suji.

Suji relies on the fact that a player is using a [[ryanmen]] wait, or a related wait like [[ryanmenten]], [[nobetan]], or [[sanmentan]]. Ryanmen itself appears in around ~50% of winning hands, which is common, but not even close to guaranteed. For example, hands like [[toitoi]] and [[chiitoitsu]] are immune to suji.

Note that the middle tiles (4,5,6) have two different suji intervals to account for. For example, 4 is part of the intervals 1-4 and 4-7. If an opponent discards a 7, the 4 isn't much safer, because the ryanmen of 1-4 is still present. In order to make 4 safer, both 1 and 7 must be safe. If both 1 and 7 are safe, then 4 is considered a nakasuji. The same applies to the other intervals.

*"Half suji" tiles, e.g. a 4 after only a 7 has been discarded, are not much safer than a regular tile.

Ura suji is a theory which suggests that: when a middle tile is discarded relatively early, unsafe suji intervals that are nearby become more dangerous. For example, say an opponent had a 35 [[kanchan]] in their hand. If a 2 is drawn, then 5 would be discarded from the "235", leaving just a 23 shape. The 23 waits on a 1 or 4, so if a 5 is discarded relatively early, then 1-4 becomes more dangerous.

In the modern day, ura suji is often disregarded. If an opponent discards 5-pin early, then declares riichi later, then non-suji 4-pin would be a dangerous tile. However, a non-suji 4-man, 5-man, 4-sou, etc. would also be dangerous tiles. Therefore, knowing about ura suji would not change your behavior.  

*If you were folding, you would not discard any non-safe non-suji tiles unless you had to.  

In addition, ura suji assumes your opponent is going for maximum [[tile efficiency]]. It also assumes that the 35 kanchan had existed in the first place. The 5-pin could have been an unrelated tile, or it could have been part of a 57 kanchan, or part of a completed 556 shape, or part of a completed 135 shape, etc.