Composite Shapes (2)

There are many kinds of four-tile composite shapes, but on this page we will focus on combinations of one complete set plus one floating tile.

There are five basic patterns in this family, and every one of them is very important.

Nobetan Shape

(Example)

This is a shape where four number tiles run in a row. There are six patterns, from 1234 through 6789, so the original page lists the acceptance for all of them.

Shape	Edge wait Closed wait	Open wait	Three-sided wait	Pair	Effective tiles
					6 types, 20 tiles
					7 types, 24 tiles
					8 types, 28 tiles
					8 types, 28 tiles
					7 types, 24 tiles
					6 types, 20 tiles

Just like single floating tiles, nobetan shapes get better the more they sit toward the center.

Please remember this clearly: 3456 and 4567 are the thickest four-tile shapes in mahjong. When you have one of them in your hand, you should count it as having the power to make two sets.

1234 and 6789 are functionally close to having a lone 4 or 9, but they have the advantage of being better at forming a pair.

In general, nobetan is a good shape and should be handled with care.

For example, in this hand, discarding and carelessly fixing the nobetan shape as a single set would be hardly an exaggeration to call extremely inefficient play.

Theory and Summary

Nobetan shapes have very wide acceptance. In particular, `3456` and `4567` are the four-tile composite shapes with the greatest power to make two sets.

Middle-Bulge Shape

(Example)

This is a shape where the middle tile of a set is duplicated.

Shape	Edge wait Closed wait	Open wait	Pair	Effective tiles
				4 types, 12 tiles
				5 types, 16 tiles

1223 and 7889 have relatively narrow acceptance and easily create bad shapes, so they are not especially easy to use.

Compared with a lone 2 or 8, their main advantages are that they are slightly better at forming iipeikou, and that when they become an edge-wait-plus-closed-wait shape, they are better at making a pair. (67889, for example, can make a pair plus one set by drawing 5, 6, 8, or 9.)

But the middle-bulge shapes from 2334 through 6778 make open waits very easily, so they are extremely useful.

Theory and Summary

The middle-bulge shapes `2334`, `3445`, `4556`, `5667`, and `6778` can make an open wait with four kinds of tiles, and they also carry the possibility of iipeikou, making them excellent shapes.

Pseudo-Ryanmen Shape

(Example)

Whether "pseudo-ryanmen" is truly the official name is debatable, but you will see this shape often.

1123 2234 3345 4456 2344 5567
3455 6678 4566 5677 6788 7899

Those are the twelve patterns in this family.

In terms of pure ability to make two sets, these shapes are not very different from a lone floating tile. (2234 is roughly like a lone 2, while 4566 is roughly like a lone 6.)

However, they have the following three advantages.

(1) Even if the shape remains as your final wait, it still works as is

Tsumo → cut and riichi

Precisely because it is a composite shape, even after the pair disappears, you can still riichi with a clean six-tile wait.

(2) It carries iipeikou potential

(3) It can develop into an irregular three-sided wait

Tsumo

Because it uses two identical tiles, the acceptance is a little thinner. But when one more tile comes in, the shape can become a three-sided wait while also keeping the pair. (In this example, that means , or anything from through .)

One-Gap Shape

(Example)

Try to become consciously aware of this shape.

In this example, the floating tile is . But if you draw , it immediately becomes the open-ended shape . Even when it only turns into a closed wait, it still has many ways to improve into a good shape, so it is much easier to use than a lone .

Shape	Edge wait Closed wait	Open wait	Three-sided wait	Pair	Effective tiles
					4 types, 14 tiles
					5 types, 18 tiles
					6 types, 22 tiles
					6 types, 22 tiles
					5 types, 18 tiles
					5 types, 18 tiles
					6 types, 22 tiles
					6 types, 22 tiles
					5 types, 18 tiles
					4 types, 14 tiles

The table above shows every one-gap composite shape.

Somewhat surprisingly, 5789 and 1235 do not differ very much from a lone 5, because the completed set sits at the edge and the shape is weak as a connected form. (Their advantage is that you can chi them into two sets, but that will always be with bad shapes.)

By contrast, 1 and 9 become much stronger here than they are on their own. The 1 in 1345 and the 9 in 5679 are even stronger than a lone 2 or 8.

Theory and Summary

One-gap composite shapes are good at making good waits, and they can also be called to make two sets at once.

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Original Japanese page: http://beginners.biz/kihon/kihon10.html

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