Tada~
In theory Ghost should be able to do some amazing inline cleverness and have this serve out a live demo too. Hopefully if you're using a normal browser (not IE) there should be a little boxy demo above.
Click on it or tap on it to move the red player box. :)
I've really been impressed with the speed and quality of PIXI.js, which is the rendering engine used here. Those guys from goodboy realllllly have it down. That's the future of the web right there.
...now if Apple will just suck it up and add webgl support to their devices we could all be friends.
Idly it's worth a note that there are piles of Box2D implementations out there, but I personally found the procedurally migrated https://github.com/kripken/box2d.js was the best in terms of documentation and speed.
Next time round maybe we'll dig through some of the guts of the box2d binnding to pixi.js, but for the time being you can view the demo stand alone here, and use the magic of 'view source' to see for yourself.