Okay, so maybe it's actually LEDs and mirrors. This is the homemade Portal "loop" created by Florian Aich using two mirrors backed with colored LEDs and mounted across from each other on opposite walls. He even uses a portal gun to "shoot" the lights on. Man, I remember growing up I had a shower that had full-length mirrors on the front and back walls and sometimes I would stand there and try to count how many versions of myself I could see. I forget how many I got up to, but by the third one my peenor was too small to see, I remember that.
Hit the jump for a brief video.
Thanks to Brisket, who once Portal'd his way into a sports bar after hours to cook his own hot wings.