Within a few seconds it was completely dark around him.

Put that book in a completely dark room and it will not appear red.

Then, suddenly, the sound turned off and the screen went completely dark.

Once it was completely dark we could not go on.

The house was completely dark except for the top floor.

It had never been completely dark, at least not that he could remember.

It was completely dark when they got back to the hotel.

It was completely dark by the time they went their different ways.

But we'll stand a better chance if it's completely dark.

If the light is weak, then a completely dark room might be needed.