multiple lights for teapot example

[sooonism]

Hi, I love this framework and I am going to use it in my next project.
Currently I have hard time to add in more than 1 light in the teapot example. I am new to shader so I am not sure where to start. I play around with the example code but it only display 1 light. I recon I have to do something at either VertexShader or FragmentShader but none seems to work. Do you mind to point out?

Where else can I get a good example on ES 2.0 lighting especially working with shader? I go through books and web and so far not getting any good result. Thanks!