For those who don't know what modern browsers can do, play this in a modern browser (that is, anything but IE). Browser Ball
Where did I find this? Umm. Actually, when you do as much research as I do, things like this show up all the time. btw, as things stand with IE8 and possibly IE9, you will never be able to do that in Internet Explorer, even though the code is part of the standard and supported by every other browser. Microsoft has given no indication of its plan to support that code.
Wow. This is very cool. The canvas support is really great. I'm looking myself to write such apps when I have more time.