L+1 group

First L+1 group  

The first L+1 group lives or dies according to who plays first.

Black lives  

Black can live by playing on the 1-2 point as shown.

Seki. Black can play 'a' to get a ko.  

Other possible defenses end up in ko or seki, depending on black's choice, as the next two diagrams show.

Same result.  

White 2 is the only move. White 2 at the vital point fails to Black 2 at 4.

White kills  

White can kill by playing hane at . This reduces the shape to the standard L group, which we already know is dead.

What now?  

What happens if White plays on Blacks vital point? (Just thinking about "Your opponent's good move is your good move" does that apply here as well? I think Black is dead as well but am i correct?

White kills  

Yes, white still can kill. After 7 - Bent four in the corner

First L+1 group, hane on one side  

The extra hane gives a sense of security.

White cannot kill this way  

The throw-in at no longer works: jumps and lives. If makes a placement, connects, and White cannot connect at a due to shortage of liberties, otherwise Black captures three to make an eye.

White kills  

However, White can kill by the hane at followed by the placement at . tries to live, but forces , so makes a throw in and kills. Note the importance of the stone.

First L+1 group, hane on both sides  

The first L+1 group with hane on both sides is alive if it has an external liberty. However, when the group has no external liberties, White can turn it into a ten-thousand year ko.

Main line  

The key tesuji here is .

Main line  

The best moves by both players lead to a ten-thousand year ko.

Main line  

Black can also get a multi step ko (for white) sequence, which should be better than ten-thousand year ko.

Main line  

White must first win this ko in the corner...

Main line  

Black can get rid of ko threats before continuing. If white wants to continue, he must play yet another ko to force the atari.

Main line  

Only now does the real ko for the life of the corner start. Black usually should be able to win this or receive ample compensation elsewhere in the steps white took.

Second L+1 group  

If the leg is on the other side, again the position depends on who plays first.

Black lives  

Now the 2-2 point is the vital point for Black.

White kills  

Again, reducing Black to a basic L group by a hane, kills the corner.

Second L+1-group, hane one side  

The hane at may seem to give some help in living.

White cannot kill this way  

The throw-in at doesn't work anymore. Black lives with : White can not connect at a because Black can capture three to make an eye.

White kills  

To kill, can go straight to the 2-2 point. After , Black is dead. See the addendum of the rectangular six in the corner page. Study: Would the marked White stone still be needed if the Black hane was at the top?

Problem  

The two hane stones give some degree of security.

Solution  

The attachment at leads to ko.

Second L+1 group  

The second L+1 group with a weak leg is also unsettled. White can kill at a or Black can live by playing at a.