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20

Suppose there is a black stone in the corner but it is impossible for black to survive, no matter how well played. By convention, both sides recognize this and the black stone is counted as a prisoner. If either side doesn't accept the convention, both sides will alternately play until the situation is resolved (in favour of white). At that point, black and ...


6

This depends on the rules used. In rules using area scoring (Chinese style), a player's points include both the empty intersections they surround, and their stones. In this case, any extra moves made inside a player's own territory do not cost points, unless there are dame left, since the move could have been used to take one and with area scoring that ...


6

It's entirely a question of efficiency: It simply takes fewer stones to secure more territory if you play in the corner. Taking, for example, the eleven stones White plays in your sample game, if Black had played the same number of stones in the corner instead: $$Bc $$ ----------------------------------------- $$ - x X . . . . . . . . . . . . . . . . . - $$ -...


5

If Black plays in that area, White could ignore it or pass and gain a point - the black stone would be agreed as dead, and White still gets the point it's sitting on. Black can only force White to surround and capture the stone if they're threatening to capture some of White's stones - for example if they cut off part of the wall, and it creates a capturing ...


4

It is a question of efficiency. In this diagram, white has indeed made a live group, taking 11 moves to surround 4 points of territory. The black stones 3 and 5 make a loose but significant claim to 30 points or more. If black had been making similar moves with the other nine plays while what was building its little fortress, it would have a much more ...


3

Summary It does not matter if a group is “surrounded” (which is hard to define); all that matters for the score is enclosed vacant points. The rules Vacant points only connected to stones of one player count as territory for that player; if “area scoring” is in use, points occupied by a player also count for them, but this seldom alters the result(!). Stones ...


3

I know this is a textbook situation, but I do not practice tsumego, so I had to read through this. It was quite tricky and took some time to, hopefully, get right. The strongest (i.e. hardest to correctly answer) resistance I found is this: $$ ------------------ $$ . X 3 5 2 . . . | $$ . X O O 1 . 4 . | $$ . X X X O O O . | $$ . . . . X X O . | $$ . . . . . ....


2

A corner invasion can in some cases can make a huge difference. In this case the play on th 3-3 point threatens to cut the white group in the upper left into three pieces, two of which have no chance at life and the third is in bad shape. That siad, I think the AI is a bit premature in declaring all these stones dead. A play by white to connect at the 4-3 ...


2

A group with two true eyes (not "false eyes") is and remains alive even if surrounded by the other player, and cannot be captured by an sequence of moves by the other player. That is what being a "living group" means. An invading stone that is not able to be included in a living group will be considered dead at the end of the game, and ...


1

I've seen and played a version of this were you put the black stones along the center lines of a regular 19x19 board so you carve out a 9x9 space. White is then supposed to create a living group inside. For players of equal strength this is approximately a fair game. I'm not sure what the result of perfect play for either side would be but I'm pretty sure ...


1

The black stone at Q18 is in a ladder, albeit a short one. If black pushes this, with R18, black will eventually be killed and white will live. R18 is a strong KO-threat, however, because if it is not answered black can kill the white group. If black plays P29 white must capture at R18. If black pushes at O19 the capture is again forced and white will ...


1

Your final line has the correct question more or less answered. It is convention to end the game because black would not be able to create a living group. What is important is that both players agree to this. A lesser-skilled player (black) may not be convinced and request to play it out. As the board sits, without visible captured (removed) stones, white ...


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