In Kat’s Tale we read:
Gilding The Invisible–This card starts out by telling us why architects tend to omit much decoration on tall building’s facades. Seems most people don’t notice anything higher than ten feet up. And apparently, this is also why the big warehouse stores like Sam’s Club and Costco don’t bother to finish their ceilings. The card then goes on to instruct us to “remember the law of the invisible ceilings” if you become concerned that you’ve left something “ruinously ugly” in your book. The reader will be so caught up in the story that they won’t even notice them.
I’m going to suggest a slightly different prompt with this. Think of something that tends to be invisible to most people during everyday life–the walls of that tall building; the ceiling of that warehouse club; the back room at a popular cafe; anything else you can think of. Then come up with a story concept in which there’s something going on in that “invisible space” that could affect everyone around it–all those people who don’t notice a thing.