Snapback Problem 4 / Solution

Scartol: It appears to me to be a ko. At feels like Black's best move -- now White is in danger of a snapback if Black plays at a. Therefore, White must connect there, in which case Black can play at b for a ko for the whole group. Alternatively, White can play at c instead of a, and Black must respond at b. Either way, it's a ko for life or death... Right?

HolIgor: Correct.

Connector "korner ko?" ;)

Bob Myers: White's correct response is a, not c. If he plays at a, after Black b, White takes at c, and Black must make the first ko threat (try to get first capture in a ko). If he plays at c instead, then Black takes at b, and it is White that must make the first ko threat.

UffeHellum I'll try to draw why white should play a before c.

CASE 1: White starts the ko first.

Now White tries a ko worth 30 points and B responds.

Now black tries a 25 point ko to continue the fun...

is allowed to capture the 25 point ko, but white keeps the corner.

CASE 2: White connects first.

Now Black tries a ko worth 30 points and W responds.

Now White plays a 30 point ko...

And Black has to come up with one more 30 point ko.

The difference between case 1 and case 2 is that Black has to spend ko threats to keep things going.