Flick of a switch controls this Earth Hour ad

The World Wildlife Fund teamed up with Hot Chip to create this cool online ad for Earth Hour. It's actually two videos in one—a "light" version and a "dark" version. The one that plays for you depends on the amount of light your webcam is picking up. (Your room needs to be very dark to play the dark version, so hold your hand over the webcam if you have to.) If you're still rocking a webcam-less computer from 2003, you can check out an alternate version over on YouTube, where you toggle between light and dark using a light switch in the upper right. (The webcam version is a lot more seamless, though, as the characters' steps match up.) I'm a huge fan of stop motion as well as non-traditional uses of online video. And by registering to turn off your lights during Earth Hour this Saturday, you get a warm and fuzzy feeling of saving the world—from a Doom Laser! It just reminds you how everything goes right when you turn off the lights.

—Posted by Christine Hall