Sorry, but if a 7 year old kid wrote this in Flash I might be impressed. JavaScript has light-years to go before it's a viable platform for anything involving animation and graphics, for even the most cursory uses.
>light-years to go before it's a viable platform
>for anything involving animation and graphics
once all browsers support the canvas element (as does firefox3) its just a matter of time until some standard 2D animation libraries popup that will enable game development.
flash is ecmascript + proprietary set of libraries and a great IDE. but javascript has the advantage of coming out-of-the-box with the browser.
With Chrome, it only started when I used enter. Nice demo of what one can do with JavaScript and modern browsers. As other people mentioned, flash still wins, but I view this as very impressive.
The code needs quite a bit of polish, but as the author mentioned this was a quick hack.