Like some others, I personally cannot sleep unless it is completely dark in my bedroom. However with the placement of my bed in a dark area of my room, I'm surprised to find that I cannot sleep because there is still light shining on my bed. But why is there still light if the window in my bedroom is behind my bed, next to a wall? Shouldn't the light be blocked by the barrier? No! The light from the window still shines on to my bed, despite the wall barrier and placement of the bed and window, b