Bike Reflector Art

I took my brother and sister-in-law to see the building I work in, late at night after dinner. There's this artwork on one wall, about 10 feet wide and three very tall stories high, made of different colored bike reflectors. My brother, Handy MacGyver, had a flashlight/laser pointer readily at hand, and he quickly discovered that if you brace the flashlight on your forehead and walk back and forth across the atrium, you see shiny waves of light crossing the piece. Of course, everyone had to try it, including a baffled professor who discovered us staggering around in the lobby. Here's my blurry sister giving it a try: