“The End” effect

So let’s explain this one: there is a clip with “The End” written in the middle, and above this clip there is the actual movie. The actual movie has a mask which represents a white (=opaque) circle on a black (=transparent) background. At the begining, that circle is so large that you see all the actual movie and you don’t see the “The End” clip. Then the circle becomes progressively smaller and as a consequence you see less of the actual movie and more of the “The End” clip.