Here are the solutions to the challenge problems from "The Game of Go". They include a selection from the most pleasing of the tactical tricks in the game, and have been chosen to help explain why Go fascinates people.
The key to this problem is to hold the forcing move at 3 in reserve. Black starts at 1, and if White plays from the left at 2 the time for 3 has arrived, and Black makes sure that there is only one eye on the left before extending at 5 to make a false eye of the one on the right.
If White plays from the other side like this, Black adds a stone at 3 and the dead black stone to the left serves a different purpose. Now White has to play at 4 to have a chance of making an eye by capturing the two stones 1 and 3, and then 5 catches White in a shortage of liberties.
White can certainly make one eye by playing at 4, and the trick is to find a way to threaten all of the eye shape on the right with one move. Black 1 is the move - if White replies at 4 immediately Black has a clever play at 5, making a 'snapback' shape which lasts just long enough to ruin White's eye.
White has two possible ways to survive here, either capture the black stones in such a way as to make two eyes, or make a 'seki' in which Black cannot fill the mutual liberties of the two groups without offering White a two eyed shape to capture.
Black 1 here is the only way to prevent both of these. Black makes one eye in the corner, so that a seki is impossible, and leaves a four stone pyramid which will only be worth one eye if White captures it. Any other Black play would allow White to play a stone at 1 and live.
(White 4 connects at 1)
The key to this symmetrical shape is patience. Black has a good combination for stealing a white eye with 3 and 5 here, and by playing the waiting move at 1 Black can hold the option of playing that combination from either side.
Black 1 forces White to try to keep the two potential eyes separated with 2. But 1 is also well placed to combine with the tiny weakness in White's surrounding wall so that Black 3 can steal the eye on the right.
(White 4 throws in a sacrifice stone to the left of 3)
White 2 here is a resilient reply, but Black patiently continues with 3, waiting until the capture at 5 will be atari on some stones on the outside so that White has no time to throw in the eye stealing sacrifice stone.
This delightful little problem seems completely impossible until you know the answer.
Black absolutely must play at 1 to have a chance of making two separate eyes. . .
Next White can try to steal the eye on the left with the sacrifice at 4, but Black takes the key point at 5, letting four stones go. . .
The space left by Black's four captured stones is now big enough for some further activity. Black 7 captures two stones and makes an eye.
This is another example involving 'playing under the stones'. Black first increases the sacrifice to three stones. .
Next White can capture at 4. . .
But when Black plays at 5 there is no time to spoil the eyeshape with 6, because Black 7 uses the dead stone in the upper left to create a liberty shortage.
(Black 3 plays back at 1, White 4 captures one stone)
Black must capture in a way which will keep White busy. Black 1 here is good enough to capture the two stones on the edge using a 'snapback' (White can capture a stone at a but Black would recapture three stones immediately).
