The descent at is key for life. If makes a placement, then and forms a seki. This is the main line.
// Isn't unnecessary? -Heikki
JoelR: It is necessary. If White gets and the point to the left of , Black's left side is in atari.
If plays the hane, then divides the eye space into two eyes very nicely. White cannot cut at a because of shortage of liberties.
doesn't live. White kills with and . Black can capture by playing at but this only creates a false eye.
I thought maybe I had seen something when I started to run these through, but soon answered my own question. is no good either.
See also: