uses -webkit-canvas (so obviously webkit only) Demonstrates using a canvas element for dynamically generated background patterns. There are ways to do this in Moz (css element) however I'm not sure about IE's capability. Tree's are rendered via canvas, see here: http://codepen.io/rlemon/pen/tBAdC
This is a simple way to detect the distance the user has scrolled on your website. You can use it to do anything you'd like. In this example, I use it to drop down a navigation bar so the user does not have to scroll all the way back up the page in order to navigate to the next area. It could also be used for sliding in a social sharing bar, displaying more content, or anything, really.