DieterVerhofstadt/Examples of reading

What can black do?  

For me, the circled points are all candidates for the first move.

First line  

First candidate: reduce the eye space. We can see there's a ko this way.

Second variation  

Can Black do better? Yes. If then . But can White do better? Yes:

Var 3B  

Same as Var 1 but different order. This made me realize White has an option in var 1:

Var 1B  

It turns out is the vital point in this position.

Var 4  

invites on the vital point

Var 5  

This exchange doesn't help.