(No. 178: Sep. 20, 1999)
Elementary level: Answer
Black 1 is crucial.
After White takes at 2, to the next diagram.
Elementary level: Answer (Continued)
After Black connects at 3, White may aim to capture
the Black stones in an Oiotoshi with 4 and 6.
But Black can take at 7. White dies.
Elementary level: Wrong Answer
Black 1 is wrong. White captures
the four Black stones with 2 to 4 and lives.
Intermediate level: Answer
Black 1 is crusial. The Black stones in the corner
connect to the outside and White dies.
Intermediate level: Wrong Answer
Black 1 allows White to capture
the Black stones with 2 to 8 and live.