Glad to see some HTML5 game dev articles up. Since this thread is bound to attract devs involved in HTML5 game creation, is impact.js any good? I find Lime.js to be severely lacking in tools to create something like a platforming game (I'd really rather not write physics and collision code).
In LimeJS you can use the Box2D library to simulate physics, you don't have to write it yourself.
For collision detection is pretty easy, as the Closure Library (which LimeJS is built around) comes with "bounding box" support to perform this very easily.
Construct 2 uses Box2d and Easel.js I believe.. I've seen a number of html5 game tutorials on tutsplus for easel.js but they mostly seem to be "copy what the dev did step by step" as opposed to really explaining things well.
Am I the only one worried about the 100x Farmville clones that will now be built by 15 year olds and spammed across the social sites. =)
Great tute though.