So in my previous blog I mentioned Box2D and WinRT.  David mentioned that there was Box2D for JavaScript, which is a great way to add physics to your project:

This won’t be your final library to build your game, but it certainly is useful if you like to slam code!  Thanks David!  You are the best.

Good library, one that used in the Scirra.com tool Construct2 that you can find at http://www.scirra.com.

This means that if you are considering creating your own WinRT based library in C++ that consumes Box2D could be better used to utilize the already converted library in your HTML5/JavaScript work.  WinRT is designed for Language projection. 

Here are links to a related //BUILD 2011 related sessions, which are somewhat out of date:

 

TOOL-527C – Building Metro style apps using JavaScript