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Composite Shapes (1)

There are only two kinds of three-tile composite shapes: the pair + taatsu composite, and the ryan-kan composite.

Pair-and-Taatsu Composite Shapes

This was mentioned briefly in the section on pairs. It is a shape where one tile of a taatsu is duplicated into a pair. Compared with an ordinary taatsu, it gains two extra tiles of acceptance that complete a triplet.

Type of composite Example Tiles that complete a set Count
Penchan + pair 一万牌图二万牌图二万牌图 二万牌图三万牌图 6
Kanchan + pair 六筒牌图八筒牌图八筒牌图 七筒牌图八筒牌图 6
Ryanmen + pair 三索牌图四索牌图四索牌图 二索牌图四索牌图五索牌图 10

With shapes like these, many players fix them too early as either a pair or a taatsu. If you fix them as a pair, you lose 4 tiles of acceptance, or 8 in the ryanmen case. If you fix them as a taatsu, you lose 2 to 4 tiles.

Example 1 七万牌图三筒牌图五筒牌图五筒牌图九筒牌图九筒牌图一索牌图一索牌图三索牌图六索牌图七索牌图八索牌图九索牌图　　Tsumo二索牌图

Beginners often seem to prefer pairs for some reason.

From a shape like this, you sometimes see people cut 三筒牌图, but that throws away the 4-tile acceptance of 四筒牌图 and also kills the chance for the pinzu shape to improve. It is not good play.

It may feel like losing 2 or 4 tiles is not a big deal. But mahjong is heavily a race in tenpai speed, so if all you are doing is narrowing your acceptance, it is clearly a loss.

The standard play is to discard 一索牌图.

Example 2 二万牌图二万牌图七万牌图七万牌图八万牌图四筒牌图五筒牌图六筒牌图六筒牌图八筒牌图四索牌图五索牌图六索牌图　　Tsumo中牌图

In a shape like Example 2, leading with 七万牌图 is also a mistake in most cases. The hand currently has only 16 tiles of acceptance, so reducing that to 12 is a very large loss.

On top of that, this hand can become Tanyao and still has pon-ten potential, so unless 中牌图 is especially awkward to deal with in the current situation, you should simply discard 中牌图.

Theory and Summary

With pair-and-taatsu composite shapes, do not fix them too early as either a pair or a taatsu. The basic idea is to keep your acceptance as wide as possible.
In iishanten, if you still have unnecessary tiles left over, then fixing this kind of composite shape as a taatsu often loses another 4 tiles of acceptance, so you should avoid it.

Ryan-Kan

A shape formed by two connected kanchan shapes is called ryan-kan.

一筒牌图三筒牌图五筒牌图　　二筒牌图四筒牌图六筒牌图　　三筒牌图五筒牌图七筒牌图　　四筒牌图六筒牌图八筒牌图　　五筒牌图七筒牌图九筒牌图

There are five such ryan-kan shapes, and all of them have 8 tiles of acceptance, exactly twice that of an ordinary kanchan.

If you look only at the number of accepting tiles, ryan-kan has the same 8 tiles as ryanmen, so it counts as a good shape. However, depending on how it interacts with the rest of the hand, ryan-kan can become awkward.

Example 3 二万牌图三万牌图四万牌图五万牌图七万牌图八万牌图九万牌图五筒牌图七筒牌图九筒牌图三索牌图三索牌图五索牌图　　Tsumo六索牌图

In Example 3, if you care only about the fastest route to tenpai, then keeping the ryan-kan and cutting 二万牌图 is the closest line. But that throws away the yaku Ittsuu. And if the souzu ryanmen fills in first, the final wait is only an ordinary kanchan anyway.

Example 4 二万牌图四万牌图六万牌图三筒牌图三筒牌图三筒牌图四筒牌图四筒牌图五筒牌图七筒牌图六索牌图六索牌图八索牌图　　Tsumo六筒牌图

Example 4 is one of those difficult cases where every discard loses something.

Both of these shapes look like they can make you hesitate. Because ryan-kan uses three tiles, it tends to make the hand feel tighter and tighter as you approach tenpai. Of course, some of that cannot be avoided.

Theory and Summary

A shape made from two connected kanchan shapes is called ryan-kan. It is generally treated as the best shape after ryanmen. It is especially powerful in the early game, but the closer you get to tenpai, the more clearly it falls short of ryanmen.

Original Japanese page: http://beginners.biz/kihon/kihon09.html

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