DieterVerhofstadt/Examples of reading
For me, the circled points are all candidates for the first move.
First candidate: reduce the eye space. We can see there's a ko this way.
Can Black do better? Yes. If then . But can White do better? Yes:
Same as Var 1 but different order. This made me realize White has an option in var 1:
It turns out is the vital point in this position.
invites on the vital point
This exchange doesn't help.
This problem needs 8 diagrams of about 5 moves deep. It's easy to miss variation 1B, think that 1 is the solution, while 3B is the main line.