For this navigation button I use movie clips instead of animated graphics like the previous examples. The primary difference between a movie clip and an animated graphic is that, whereas animated graphics work with the main Timeline, a movie clip uses it own Timeline. This means that regardless of what is happening on your main Timeline, the movie clip will be run unaffected. Consequently, in the main Timeline of this movie, only one frame is used. Movie clips are useful in situations in which you need to continually loop an animation or, in our case, a situation in which we need to control animations on mouse rollover and rolloffs.