| Position 1 Unfinished |
Position 2 Black finishes off |
Position 3 White takes advantage |
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The concept of fully surrounded and completed territories is not a very hard one, as already mentioned. It should probably suffice to present you with a few examples of finished and unfinished territories for you to get a good feel of it. Together with showing you the examples of unfinished areas, I will also demonstrate how to finish them off as well as what kind of things can happen if you fail to do so.
There are basically three kinds of unfinished territories which have one-point wide "holes in their walls". One of them, the simplest, has the hole in the middle of the wall. The other two deal with holes on the edge of the board. Lets look at all three of them in sequence (Examples 1 to 3.) Then we will look at some more complex examples.
This is the simplest form of unfinished territory. The "hole in the wall" is in the center of the wall, and it is relatively easy to plug it. The cost of a failure (i.e. letting your opponent push through) is not very high, only one point (since the black territory is one point smaller in Position 3 than there is in Position 2.)
| Position 1 Unfinished |
Position 2 Black finishes off |
Position 3 White takes advantage |
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Look closely at the Position 1 of Figure 1. Do you see the point marked 'a'? This is a hole in the wall, or fence, which determines Black's territory. As long as this hole exists, the territory is not yet complete, and so cannot be counted as Black's points. To be able to claim his points, Black needs to finish off the wall, as shown in Position 2. This completes the territory and gives Black 36 points. Now (s)he can pass.
But what would happen if Black fails to plug in the hole as shown in Position 2? White can certainly take advantage of this failure and push through with '1' in Position 3. After this, Black better get his/her act straight and block at '2', or White will be able to push there thus reducing Black's territory even further! This would be very bad for Black. After Black blocks at '2', he is left with only 35 points of territory, and thus the failure to block at '1' and the subsequent exchange was worth 1 point as compared to Position 2.
Please note - in Position 3, Black also has to worry about the weak points marked 'b', which might (or might not) lead to more losses if not defended - so, if Black decides to defend there, (s)he might lose more than 1 point by failing to block a '1' in Position 2. But more about such weak points later.
A slightly different example but with the same underlying idea is when both sides have matching holes in their walls. In such case, whoever plays first makes the gain and the whole turn around is 2 points (please compare the respective territories in Position 2 and Position 3 of Figure 1a.) I will leave this example without any further comment, i am sure you can figure it out by yourself. :)
| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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The second example deals with a hole at the edge of the board. Please note that the hole is both-sided, which means that both Black and White are in the same position - and whoever plays first makes a gain.
| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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This example is very similar to the one in Figure 1a, except that the side which loses points (White in Position 2 of Figure 2 and Black in Position 3) has to still defend at '4'. This means that the overall turn-around in terms of points is 4 points for the side that plays first. So a move at '1' (in Position 2 or in Position 3) is worth 4 points. You can determine it by looking at the value of territories in both positions.
By comparing both final numbers (11 and 7) we can see that the difference is 4 points. (The same kind of calculations lead me to determine that the value of '1' in Figure 1a was 2 points.)
Note:
It is also usual for either side to defend at 'c' instead of '4' in the respective positions.
Why it is necessary to defend there at all is explained here.
The final one of the one-point-hole examples is one in which the whole is on the edge of the boards as well, but unlike in Example #2, only one side has it.
| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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This is potentially the most expensive example. As we can see, in Position 1 of Figure 3, Black has a hole at 'a' while White's territory is already completed. If it is Black's turn, (s)he can play at '1' in Position 2 and thus secure the territory. Now pass and score - Black has 36 points, White has 27 points, so Black wins by 11 points.
Now, lets see what can happen if Black fails to complete the territory by playing '1' in Position 2. The result can be seen in Position 3 of Figure 3. It looks like a disaster for Black. A short calculation can verify that Black is still winning, but only with 1 point! Which means that failure to play '1' in Position 2 cost him/her a full 10 points!!! This is a big loss!
Note:
Even though Black is still leading by 1 point on the board in Position 3 of Figure 3, if the game
was played with any kind of komi (explained here), the mistake might well have
reversed the outcome. A very common value of komi is 5.5 (or 6.5 and even 8 points komi are
common on small boards) - which means that in Position 2 of Figure 3 Black would win by 5.5 points,
while in Position 3 White would win by 4.5 points! Think about that!
Let us finish this page by looking at some more examples. I will not give any comment for them, it is up to you to think and make sense of what you see. Consider it a quiz. :)
In each case, Position 2 and Position 3 are final positions, in which both players can pass. I strongly encourage you to figure out how many points each of the plays is worth!
| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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| Position 1 Unfinished |
Position 2 Black plays first |
Position 3 White plays first |
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And finally, as the last illustration of finishing off the edges of territories, let us look at a more practical position and the moves made by both players at the very end of the game. Below are the final two diagrams from the example 9x9 game I presented here during the discussion of Go Rules. The exact step-by-step scoring of the end position can be found here (using territory scoring method) and here (using the area scoring method.)
| Position 1 Example position |
Position 2 White moves first |
Position 3 ...continuation... |
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