Remember the proverb:
The corner is golden, the edge silver and the centre is a public garden.
This had been introduced in the article "Playing his first games" where I explained that during a go game, most of the time the first moves are played in the area. In this article, we will present three common corner moves and for each one an interesting sequence of moves to play.
C’est un des coups les plus joués dans le coin, il est situé sur le point 3-4 (ou 4-3) du goban. C’est un coup assez territorial, qui vise un bord en particulier.
We can see here that this move is closer to the top edge than to the right edge. This is because it aims to build a territory in the corner and the upper edge. Black can then "lock" the corner by adding a move, as shown in the diagram below. It is said that it performs a shimari, a Japanese word that can be translated as fortification.
On voit sur le diagramme ci-dessus que noir, avec seulement deux coups, a construit une bonne position dans le coin qui lui permet d’entourer grossièrement 12 points. Comme c’est un bon résultat pour lui, blanc va très souvent essayer d’empêcher noir d’obtenir une telle position en approchant le coin.
Après un shimari, noir peut viser un autre point pour étendre son territoire, représenté par la pierre marquée dans le diagramme suivant :
Pourquoi une telle pierre est-elle intéressante pour noir ? et pourquoi ici sur le bord supérieur et pas le bord droit ?
Tout simplement parce qu’à partir d’une telle position, noir a ensuite un très bon coup permettant de faire une forme de « boîte » et entourer un large territoire, comme sur le diagramme suivant :
If black decides to do the same technique on the right edge this time, the position would look like the one in the following diagram. In this case, we see that the form of black is more open than the previous one and therefore that the territory surrounded is much less secure. Its form is less efficient! That's why this side is less important for black.
After these different examples, it is understandable that Blanc would try to prevent Black from developing such training. To do this, he can play close to the points where black wants to play.
When black has only its stone on the komoku, white can approach it as on the next joseki, by playing move 1. white thus prevents black from forming a shimari. Then, with move 2, black prevents white from coming into the corner. White then tries with move 3 to keep black in the corner and aims to develop on the right edge. Black protects his stone 2 with move 4, white protects his two stones with move 5. Then black plays move 6 to expand on the top edge, and white plays move 7 to expand on the right edge.
Here, black keeps its corner, but it will have more difficulty developing a large territory and white has taken a position on the right edge. It's a fair exchange for both players.
When black already has a shimariwhite can simply play on the middle of the edge targeted by black, as on the following diagram with white stone 1!
Thus, black will have more difficulty developing on this edge. The white move 1 is often very important to prevent the black position in the shape of a "box".
This is a relatively uncommon move in the area compared to hoshi and komoku, as it aims above all to build points on the edge and not in the area. It corresponds to point 5-4 (or 4-5) of the corner, represented by the black move in the following diagram.
As said before, it is a move that targets more the territory of the edge, especially the one to which it is directed (the right edge on the previous diagram). Moreover, because of its high position, it is a move toward influence. Black waits here for white to enter the corner so that he can confine it and build influence towards the edge and the centre.
If white does not do anything, however, black can close the corner with a second move, as shown in the following diagram:
It then forms a shimari in the corner which is more open on the right edge than the one seen previously with the komoku, and therefore easier to invade for white. As before, black aims to make an extension on the upper edge in order to build a territory in the shape of a "box".
To block the formation of such a shimari, white reduce the potential of black in the corner, as on the very simple joseki of the following diagram:
It is a joseki where white reduces the black corner while building a position on the upper edge. Black keeps points in the corner, then extends to the right edge. It is a joseki that avoids complications for white, which would occur if white would invade directly on the point of the komoku, below the takamoku. Here is the joseki that could occur in such a case (complications occur with the black move 4):
Ce joseki est un joseki de combat, car ensuite blanc est séparé en deux groupes qui devront se battre pour survivre. C’est pour ça que le premier joseki est plus indiqué dans un premier temps, car il est plus simple et évite des complications.
It is also a relatively uncommon move in the area compared to hoshi and komoku, as it aims above all to build points on the edge and not the corner. It corresponds to point 5-3 (or 3-5) of the corner, represented by the black move in the following diagram.
Comme dit précédemment, c’est un coup qui vise plus le territoire du bord vers lequel il est dirigé ( le bord droit sur le diagramme précédent) que le territoire du coin. De plus, de part sa position basse, c’est un coup porté vers le territoire, et non l’influence comme le takamoku. Noir vise ici à s’étendre sur le bord droit ou construire un shimari dans le coin comme sur le diagramme suivant :
We find here the shimari seen in the part on the komoku. To avoid that black gets such training, white can come in the corner as well as on the following joseki:
Here, white takes a position on the upper edge and the corner, black builds influence towards the right edge. Then, it aims to make an extension on the right edge to build territory. One of the continuations of this joseki can be the following:
This is a long continuation here where, after black has made an extension on the right edge with move 6, white tries at most to prevent black from building a larger wall while confining white on the edge. For this reason, the white move 7 is important, and then follows until 16. White succeeds in reducing the black territory while building influence on the upper edge. If white does not play move 7, we can expect the following sequence:
(White 7 is played elsewhere)
Here black easily develops its wall because white must respond to moves 8 and 10 of black or risk being locked on the edge. Then with move 12, black elegantly develops its influence towards the right edge of the goban. The potential of black is much greater than that of white!
With these two articles on the corner we were able to fly over the 5 most played moves in the corner during a go game and their implications. Once again, knowing a few josekis is interesting to have landmarks when playing in a corner. That's why I recommend the site josekipedia, which includes a lot of different joseki. It will help you to deepen your knowledge in terms of joseki!