As far as I know nobody has written such documentation yet.
What function call(s) of the library is/are not understood?
If I look at the names of the functions in http://code.google.com/p/lolshield/source/browse/trunk/lib/Charliplexing.h
and know they are defined in the context of a led-matrix they almost explain themselves. So?
(read a bit about the LoL shield)
The basic thing you can do is set a led on or off, that is exactly what you want for snake. Which leds make up the head / tail of the snake as these are the leds that need to flip(). For Snake you will also need the status of the leds to detect the snake eating itself or one of those thingies the snake eats. This collision detection is not in the lib so you could add that yourself or ask Jimmie to do it for you or define a "shadow matrix" that holds the state of all leds. I guess the pong example needs collision detection too so you might distill it out that code.