Features of Light and Darkness demonstrates how the appearance of colors changes in different lighting conditions. In particular, it shows how the appearance of pigments changes depending on the light source that is shining on them, and it shows how human color vision changes as night falls: In twilight, the human eye can perceive color differences that are undetectable in either brighter or darker conditions. You get to choose from a wide variety of built-in light sources and pigments, and there is an editor that allows you to make additional ones.