I was coming back from walking on the trail with my stepson and saw the sky reflecting in the water along the bridge. The dam near by was pumping out a lot of light giving the night sky a purple hue to fading into a dark blue. The dam cast light onto the near by mountain and lit part of the underneath of the bridge. I took a a large flash light I had with us and painted in the bridge. I wanted it to gradually change, so as I was casting light I limited how much went into the distance.