In 1910, psychologist Max Wertheimer had an insight when he observed a series of lights flashing on and off at a railroad crossing. It was similar to how the lights encircling a movie theater marquee flash on and off. To the observer, it appears as if a single light moves around the marquee, traveling from bulb to bulb, when in reality it’s a series of bulbs turning on and off and the lights don’t move it all. This observation led to a set of descriptive principles about how we visually perceive objects. These principles sit at the heart of nearly everything we do graphically as designers.