This is Unreal Engine, with physics, cloth simulation, particles, light & glare effects. It's not C++ on Native Client or a plugin, it's running in javascript. Just yesterday you couldn't draw a circle on a 2d canvas at 30fps.
> "This is Unreal Engine" - a subset of it
> "with physics" - did not notice any falling kickable boxes and such
> "cloth simulation, particles, light & glare effects" - impressive, but there will be twice less of that then via native code
> "It's not C++ on Native Client or a plugin, it's running in javascript" - what's the difference between downloading one/two specific browsers or making a build of each with a flash player bootstrapped?
> "Just yesterday you couldn't draw a circle on a 2d canvas at 30fps" - so instead of pushing to make a universal VM, they decided to use a dynamic prototype-OOP language just because it happened to be most common - not very impressive.
Firefox has a separate ahead of time compiler for asm.js that isn't a JS VM.
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).
It works in any browser that has solid JavaScript and WebGL support. Audio will work with Web Audio, but it'll gracefully not have audio effects if it doesn't. There's no Firefox specific magic here. If you're on Aurora/Nightly, then you get asm.js/Odinmonkey optimizations and it runs even faster; that's it.
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
/be
