Tderz/Sandbox

 

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hallucination ko variation  

tderz: I would like to introduce variations about the (un-)equivalency of this immideate . What will happen after black connects at a.

several kos  

tderz: I consider this a 'virtual' ko, e.g. at a-b a/o c (there is even a variant wit a ko at d.

It is a question of skill to correctly define the status of that group and see that there is a ko involved here.

Yet this example demonstrates too that 'dead ko' is not a prima facie-derivable characteristic from a very local position, rather an end of a thinking process, more precisely the one if both players play technically most correct^[5].

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Is that the Solution?
or that here?

tsumego  

How should black respond to ?

corner  

Black cuts with . How should white respond?