I'm trying an experiment. I got some large bath towels,
What I'm discovering is that it's amazing how much those towels help darken my bedroom at night. See, living way out in the country as I do, there's a yard light out back; and the light from that yard light, even reflecting off the side of the church next door and shining through the closed window blinds, is enough to light up my bedroom at night almost as much as if I lived in a city with city streetlights.
I thought I'd try an experiment with the towels, hung over the windows, hung over the closed blinds. And sure enough, my bedroom is now dark enough at night that I can only just barely see my hand in front of my face. Reminds me of when I lived out West, in the Cascade Mountains of Washington State, many years back, and I was renting a basement apartment from someone, and once I turned out the lights at night it was pitch black, and I literally could not see a thing.
Of course, there's the question of stumbling over something when I get up in the middle of the night. But, like I say, it's an interesting experiment.