Topic: Shiny rotating cube with canvas using gradients

I happened across this script where a rotating cube with nice perspective was being shaded by using hex code which I have zero clue about. I just haven't bother to learn it. Anyway, I decided to try something with gradients and I like the effect. It's like the cube is shiny.

Here's the original script on this page
http://d.hatena.ne.jp/uupaa/20080217/1203232559
and here's a working example
http://h1.ripway.com/tinyscript/glossycanvas/test3dcubeoriginal.html

and here's the shiny rotating cube.
http://h1.ripway.com/tinyscript/glossycanvas/test3dcube.html

I was hoping you experts could think of a better way to locate the points of the gradient. I just took a stab in the dark thinking each poly would be filled by some start points and the vector end points. It looked pretty cool so I figured I show it to some people who understand the code in the hopes you could explain how the hex code works. Like I said, not even a clue on my part about that stuff.