And it only works in Firefox, and even then only very well in Firefox Nightly.
Those points aside, though, this is pretty amazing. I fully expect multiple engines to target HTML5 in the same way Unity/Unreal/etc were cross-compiling for the Flash runtime. It's just not quite there yet...
(And it's good that demos like this exist to put pressure on browsers to fully support them).
Edit: UE3 was chosen because it's known stable and optimized tech. This isn't the pinnacle of what can be done, far from it. But neither us (Mozilla) nor Epic wanted to be working with code that was still under active development for a next generation engine while simultaneously trying to port it to a new experimental platform. One step at a time! :p
And atop of missing some things from UE3, Citadel is designed specifically for limited devices.
While still a very impressive feat, let's not confuse this with running GoW or The Samaritan demo in the browser.
And it's using the exact same code as this demo. You literally use the same compiled JS, and just swap in a different set of game assets.
Thanks! (also thanks for JS, it is neat!)