Standard Corner Moves
1. Standard Corner Moves
There are 5 standard corner moves. Disregarding all the symmetrical points, the 5 of them are given in Fig 1-1. All of the have names, which are: '1' is called san-san (which in Japanese means three-three), '2' is called hoshi, '3' is called komoku, 4 is called takamoku, and finally, '5' is called mokuhazushi.
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Each of these stones has certain strengths and certain weaknesses. Each of them has also its direction - which is the direction is works towards (or direction in which it offers the most support). These differences are briefly discussed below.
2. The (3-3) Point (San-san)
| Position 1 | Position 2 | Position 3 |
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The strength of san-san is that it takes complete control of the corner with only one move. When placing a stone on san-san, a player seems to be proclaiming - this corner is mine! What happens if white tries to sneak underneath the san-san to take control of the corner is shown in Position 2. As you can see, white's attempt ends up in failure - and his stones are in bad shape.
The weakness of san-san is its low position. While it takes control of the corner, it allows the enemy to, relatively easy, play on top of the san-san stone confine it to the corner. A simple sequence is shown in Position 3. This greatly diminishes the influence a san-san can exercise on the rest of the board. Why is it so bad to be confined to the corner you can read here.
The best point to play to offer a san-san some support are the 'a's in Position 1 of Fig 2-1. The best ways of attacking a san-san is to play on 'b' or on either one of the 'a's.
Because it is low and takes good control of the corner, san-san is one of the favorite points to play on a 9x9 board (the other good one is komoku).
3. The (4-4) Point (Hoshi)
Position 1 of Fig 3-1 illustrates a hoshi stone - which seems to be the most popular of corner openings, at least on the 19x19 board. It is an ideological opposite of san-san - it is strong where san-san was weak, and it is weak where san-san was strong. Hoshi is directed towards the center.
| Position 1 | Position 2 |
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The strength of a hoshi stone is that it extends its influence into the center and along the sides. It is a very influence-oriented stone. It is very hard for white to confine a hoshi stone into the corner - or at least without giving up a huge amount of solid territory, so it is seldom even attempted.
The weakness of a hoshi stone is that it fails to firmly control the corner area. It is very easy for white to play underneath the hoshi stone (at san-san, for example) and take the corner away from him. One of the possible sequences are shown in Position 2. However - as can be seen in Position 2 - the price white has to pay for such invasion is that his stones are separated from the rest of the board and black's influence towards the center and the sides increased dramatically. For this reason, white is seldom eager to invade a hoshi stone, and even then, the exact moment in which to invade is crucial - you have to make sure first that you have a way to neutralize black's thickness somehow.
The points that work well with a hoshi stone are the 'a's in Position 1 of Fig 3-1. You can also try to strengthen the corner area by playing a tight extensions at one of the 'b's - and this is often done - but you have to be aware of the fact that even then you cannot claim the ownership of the corner since there are still ways for white to sneak in! To be able to extend influence along the side and also secure the corner with one additional move you have to play one of the other 3 moves! To attack the hoshi stone, the opponent would play one of the 'b's.
Because of its height, hoshi is not often played on a 9x9 board.
4. The (3-4) Point (Komoku)
Komoku is the second-most popular corner opening. It is somewhat of a hybrid between the hoshi and the san-san points. It is shown in Fig 4-1 - and this komoku is directed towards the right side but also towards the corner.
| Position 1 | Position 2 | Position 3 |
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The strength of komoku is that it kills two birds with one stone - it extends its influence along the side (the right side in our particular example) and it also takes control of the corner! Komoku is a very versatile and flexible point, and you can devise many different strategies based on it.
The weakness of komoku is that, while it controls the corner and works along the side, it does neither of these things quite as well as a dedicated stone would do. In other words - san-san controls the corner much better, and hoshi is much stronger towards the outside. So komoku is a sort-of "neither here nor there but everywhere" kind of move. Still - it is a good compromise between territory and influence - and so you can see it played very often.
To secure the corner territory, you may play a stone at one of the 'a's in Position 1 of Fig 4-1. These are also points at which to play to attack a komoku. There are many standard sequences which can be used to attack a komoku (such sequences are called josekis in Japanese - but only if they produce the best possible result for both sides. Otherwise, they are called blunders, hehe). Some of these sequences end up with black controlling the corner while white has the influence to the outside, some of them end up just the opposite - with black having the influence and white controlling the corner. Some of these sequences end up in terrible cat-fights with windows being broken and furniture flying around and nobody being sure who controls what! Hehe... komoku is a funny point this way. Two of the more peaceful corner sequences (josekis) involving komoku are shown in Position 2 and Position 3 of Fig 4-1. In boith cases black gets the corner while white gets a slice of the side. But there are other sequences which end up with opposite results.
Komoku is one of the favorite openings on a 9x9 board (the other is san-san).
5. The (4-5) Point (Takamoku) and the (4-5) Point (Mokuhazushi)
Takamoku and mokuhazushi points which are even more outside-oriented than a hoshi. They can be seen in Fig 5-1 (Position 1 and Position 2 respectively). The direction of the takamoku (Position 1) is strictly towards the center, white the mokuhazushi (Position 2) acts towards the side (towards the right side in this particular example).
| Position 1 | Position 2 |
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The strengths of these stones is that they are even more influence-oriented than the hoshi. It is impossible for the opponent to confine them into the corner - as with hoshi, an attempt would mean giving too up much of a solid territory). What usually happens is that white jumps into the corner and is satisfied to live there while black build up a massive thickness and influence (or vice versa if the colors are reversed). Examples of such sequences are shown in Fig 5-2 (Position 3 for takamoku and Position 4 for mokuhazushi). From this example (Position 4) it can be also seen how the mokuhazushi extends its influence towards the side! Position 5 shows a seldom playes joseki involving mokuhazushi in which black gets to keep the corner while white extends along the side.
| Position 3 | Position 4 | Position 5 |
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The weakness of these two points is that it makes it very easy for the enemy to penetrate the corner - and not only that, he can also get a much larger and more comfortable corner territory than when attacking underneath hoshi (or komoku). Another weakness of takamoku and mokuhazushi is that they do not have the flexibility of hoshi and komoku - if you play takamoku or mokuhazushi you pretty much declare what your overall game strategy will be - where you want to have your territories and which area you are willing to abandon. This may allow the opponent to devise specific counter-strategies well ahead of time, and this can be dangerous. Bottom line - do not play these moves until you are comfortable with them and until you know exactly what you're getting yourself into.
Good ways to attack takamoku and mokuhazushi are denoted by 'a's in Fig 5-1. These are also good points to strengthen the corners. This is with agreement with the principle that The opponent's key-point is also your own key-point. Which means that whatever is a good point for your opponent to play, it is usually also a good point for you to play, and vice versa.
Neither takamoku or mokuhazushi is often used on 9x9 board - and this is not because they are bad points, but because of the small size of the board - a point like this will more in the middle of the side than in the corner, hehe...
6. So - what else is out there?
Not much! There are some players who experiment with strategies based on points like [6,6] or [6,7] or even [6,8]. Some good but not too popular strategies are based on playing at the tengen point (tengen point is the central point of the board, the middle of the sky) - and this is often seen on 9x9 boards but not that often on 19x19. Aside from that - feel free to experiment on your own. Who knows, maybe you will stun the world one day by devising a revolutionary strategy? Or maybe not, hehe... For now - just have fun!