L+2 group with descent
L+2 group with descent I
It is said that the L+2 group is alive. However, when there is a descent at , it is not exactly the case.
The tesuji
What works for the L+2 group case does not work here. The atari at is a mistake. After
, due to shortage of liberties, White is unable to prevent Black from connecting the three stones at a.
For Black to win the ko, he must make two moves at and connect at
.
Method II: A better method?
Bill proposed that Black can hane with and start a ko with
. This is a two stage ko for Black, and White has a ko-threat at a. In most cases, this method is slightly better than the previous method.
When Black wins the two kos, Black connects at to finish White off.
Alex: Looks like a good way for a Moonshine Life position to arise. Now White just needs to arrange for a double ko somewhere else... :-)
Method III: When both sides have no ko threats
When neither side has a ko threat, this is best. Note that both players threaten to make a ko. This is like a ten thousand year ko, either player can convert to a proper seki.
L+2 group with descent II
The descent at does not affect the status of the group, which means that White is unconditionally alive. Defence against Black's attacks are identical to those listed in L+2 group.