I don't know, the first took me two seconds, the second five and the third five too. I stopped reading there because the article says next ones are harder and I would like to take a quiet time to read the whole thing.

I use to solve chess problems at lichess, a similar concept. Maybe.

Is it really an infinite haystack? It's context. And simplest solutions first, gradually think of more complicated ones. First try to find a pattern visually, then use simple concepts, then more complex concepts.