Beginningless #3: The striking of thunder has opened the gate of the head's crown.

Koan:

Seikenko of Cho composed a gatha as he was enlightened upon hearing thunder strike.
Sitting in the room in absolute silence.
Mind-source unmoved, filled like still water.
The striking of thunder has opened the gate of the head’s crown.
The beginningless self-nature has been awakened.
Present the implication or content of each line.”

I like the expression “you hit it on the head.” And not only the crown, but the protuberance on the top of the head representing the status of being a Buddha. And yet, this is only an entrance, a door.