Using .as files in a Flash Game

Hello,

I am quite a beginner to Flash CS5 and ActionScript 3.0, I worked mostly with the good-old Macromedia Flash MX 2004. Recently, I had a school assignment to make a flash project, in which I created a basic game that sort-of worked, but it amazed my teacher anyway. Now, since I still have the characters and graphics, I would like to redo the game in a more professional manner (not like: placing 50 lines of AS3 in one frame, inside a MC, inside another MC, inside another MC, which was all under a mask on the main stage). What I would like to do is write '.as' files to contain the AS3 script and other components of the game.

I have found that Flash Builder 4 is a good tool for writing code, but I don't know (or understand) how the code can mix with the Flash timeline and MovieClips? (Like what does the word 'extends' mean in a package?, and what is the function 'super()'?). If anyone can lead me to a tutorial, a book, or just provide a post that can help me understand how ActionScript files are incorporated into flash, I would be very thankful.

Please, any knowledge to help this beginner is appriciated.

Thank you,

Greg