Rebound: On / Off Toggle

Here's the on/off toggle I posted earlier, in actual working code. It's a class on a <label> that wraps around a visibility:hidden checkbox. JavaScript looks to see if the checkbox is checked or unchecked, and adjusts the background position accordingly.

You might wonder: Why not just use a checkbox? We wanted this UI to imply immediate effect, rather than the user wonder if they needed to go click a submit button somewhere.