Ponnuki

Capturing to make a Ponnuki  

A ponnuki is the diamond shape produced after capturing a single stone. Some people refer to it as a flower, as in the Chinese term.

This move and its resulting shape is considered strong, radiating influence in all directions. It is so strong that the proverb says "A ponnuki is worth thirty points". In practice this heavily depends on the actual position, of course.

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Efficiency

A Ponnuki is considered a strong formation because it has a solid thickness and a good potential for forming an eye. Its strength comes both from its shape, and from how efficiently it is made. In effect, Black uses only three moves to create a four-stone formation—if we count the first Black move and the White stone as a single exchange.

If Black forms the diamond without capturing an opposing stone, the result is less efficient and would not typically be called a Ponnuki. Although such formations occur, it should not be aimed for.

Genuine Ponnuki

Less efficient Ponnuki

More efficient Ponnuki

Having an extra (fifth) stone makes the formation less efficient because the extra stone does not contribute enough to justify the additional move. Some players do not even consider this a true Ponnuki. On the other hand, if capturing one stone leaves a second White stone without much potential, it can make the Ponnuki even more attractive—suggesting that White may have wasted a move (see diagram).

In an actual game, positions do not exist in isolation. The Ponnuki usually appears near other groups and during complex fights, so its overall strength depends on the specific situation. As for all good shapes, each of the moves that form a Ponnuki should only be played if it fits the flow of the game. In cases where forming the Ponnuki does not create any other strategic benefits, Black might choose not to capture the White stone, possibly leaving it in Atari. Some people, such as Guo Juan in her online school^[1], prefer to reserve the term ponnuki for cases where the shape is indeed powerful.

The example below shows a scenario where every move is necessary, and the Ponnuki forms naturally.

Example

A joseki  

Resulting position with the Ponnuki  

In the double-hane variation of the 3-3 invasion joseki, a Ponnuki appears. While this variation is generally seen as balanced, some players are critical of it for Black because of the aji in Black's overall position and the strength of White’s Ponnuki. These factors can outweigh the territorial benefits in the corner.

See also

• A ponnuki is worth thirty points
• Diamond
• Tortoise shell

Notes

[1] See her Terminology lecture 2 at https://internetgoschool.com/auth/lectures/1794.lecture?, at time 06:10.