The go game is a game of shapes that are drawn on the goban during the game. We will see in this article the following usual forms:
- Nobi, Tobi and Nikken-tobi
- Keima and Ogeima
Nobi, Tobi and Nikken-tobi :
The Nobi is the shape taken by two stones of the same color sharing a liberty, as shown in the diagram below. It is said that these two stones are "connected".
This shape is very solid, because white cannot disconnect these two black stones. But it is also a slow shape, because it covers only a small amount of space on the goban.
Tobi is the shape taken by two stones of the same color separated by an intersection, as shown in the diagram below:
It is a faster shape than Nobi because it covers a larger space with the same number of stones. It is also more flexible, as one of the two stones can be captured without the other being captured because of the intersection between the two stones. But this intersection makes it a less solid shape than the Nobi.
In the above sequence, white creates two cutting points in the black shape (marked intersections). These two points are locally miaï: these are two equivalent options. If black connects on one of the intersections, white can play on the other and cut a black stone. It is a sequence that allows white to cut a black stone, which underlines the slight fragility of the Tobi.
Miaï: term designating two equivalent options.
Nikken-tobi is the shape taken by two stones of the same color separated by two intersections, as shown in the diagram below:
It is a faster form than Tobi (and therefore even faster than Nobi). It is very flexible and is used when you want to run quickly out of enemy territory. The two intersections separating the stones make them a weaker shape than the Tobi, easily separable. It is a shape that favours lightness over solidity.
To cut this shape, white can choose between move A or B in the diagram below:
Par exemple, Blanc joue A et tente de couper les deux pierres noires. Si noir essaie de connecter ses pierres, il en résulte la séquence présentée sur le prochain diagramme, où noir est coupé en deux (ainsi que blanc). Il peut ensuite capturer la pierre 3 en shicho avec un coup en 6, mais alors blanc peut jouer 7 et couper la pierre noir marquée.
White can also choose to take out stone 3 if the shicho is not good for black (see course on shichos) as shown in the diagram below. Black must then pay attention to the cut (marked intersection).
Keima and Ogeima:
The Keima, or horse jump, refers to knight's move, the movement of the knight to the shogi. This is the shape taken by the two black stones below:
In the same way as the Tobi, this move has weaknesses in A and B. White can therefore try to cut the Keima by playing in A or B, depending on the surrounding situation. Let's see what happens when white plays in A:
Black tries to connect his stones with 2, white plays 3 and cuts the black stones. But black can play 4 and take stone 1 in shicho. So white must be careful with the shicho before cutting!
If white cuts with B, the shicho will be on the other side (by rotating 180°). In this case too, the shicho is to be taken into account.
Thus, Keima is strongly linked to the shicho techniqueit is therefore important to master this technique well.
The Ogeima, or great horse jump, is the shape taken by the two black stones below:
Ce coup est pour le Keima ce que le Nikken-tobi est pour le Tobi : il est plus rapide, plus léger mais possède donc plus de faiblesses, car l’espace entre les deux pierres est plus grand. Il est donc plus facile pour blanc de le couper. Voici une des façons :
White plays 1 and black tries to connect its stones with 2, then white cuts in 3 and finally black cuts in 4. we see that if white develops one of its stones with 5 for example, black can capture the other in shicho with 6. these two options are miaï. So to play this sequence, you have to be careful with the shichos in the same way as with the Keima.
Of course, all the sequences presented in this article are only examples, it will happen in your parts that you come face to face with other sequences. In this case, you will have reference points to which you can relate to feed your reflection.
You will find below a short interactive summary of the course, good game for you!