When I was in elementary school, my brother and I had sleepovers at Grandpa and Grandma's house. After we were sent to bed, I could hear the TV on in the other room. I heard many things ---inclusive of, "lurking in the shadows".

That left me with a somewhat lasting impression ...which traveled with me through the years.  When I went to college, as an elective, I took a beginner's Art class.  For several weeks, all we did was shading.  That changed my perception of things ...particularly, shadows.  If everything is light, there is no image.  The light and shadow reveal contrast.  It begins with an outline, and the more shadows ---the more depth.