Flash Scrolling Backgrounds

I had to make some ‘eternal’ scrolling backgrounds for Flash Games in the Foundation BSc Multimedia 2^nd years program. I found a great tutorial at the ever wonderful Flashkit, with a moving plane as a bonus. Very nice. The simplest idea, when you understand it, is how the background works. Two backgrounds, both movie clips, (exaclty alike), are placed end to end in a mother movie clip. The first one covers the stage, the second waits to the left, (or right) off stage. Using actionscript, the first moves along, and the second then follows it. At a given point off the stage, the first one then reappears ‘behind’ the second one, as that is now the one in view on the stage. So simple, yet initially hard to grasp when you try to get it without clues.