the upstairs light is on in Bob's castle
Or this version of Earth Centre NGO Vleeptron.
I worked in a couple of bookstores, and one of them was in a shopping mall, and our meat-and-potatoes bread-and-butter line were Harlequin Romances, a.k.a. Bodice Rippers. Harlequin has a different Brand Name for its Racier Stuff, where the Rake and the Maid actually get something physical going before tying the Bonds of Holy Matrimony.
Anyway, I got pretty good at ordering The Kind Women Like, at understanding which ones flew off the shelves, and which ones just sort of grunted and stayed there.
And it was a very curious sub-industry about which I was totally clueless, so I paid attention to the details.
Most Romance Novel covers depict a beautiful terrified young woman fleeing from a dark, brooding castle in the dark depths of the night.
About 30 years ago, an art director made an astonishing fundamental discovery.
If you keep one window lighted in an upper floor of the castle, but all the other windows are dark, that title sells 50% more copies than an identical cover with several castle windows lighted up, or all the windows dark.
So now all Romance Novel castles have just one light on in an upper window, from which the beautiful young woman flees in terror in the dark depths of the night.
Why is this? You tell me. No Pizza. I don't know the answer.
Anyway, just one window on now in Earth Centre NGO Vleeptron.