There are mainly three types of symbols available in Flash CS3. These are Graphic, Button and Movie Clip symbols. Each symbol has got a unique Timeline and Stage. These symbols can be applied many a times in a document, or even in other documents. Graphic symbols are used for static images. Another imporŽtant us'age of Graphic symbol is to create reusable pieces of animation that are linked to the main Timeline. In comparison to buttons and Movie Clips, Graphic symbols contribute very little to the flash file size as they usually don't have a time line with animation as such. These symbol functions in sync with the main Timeline.
Button symbols 5 on the other hand are mainly used to create interactive movies. These buttons respond to mouse clicks, rollovers and other actions. Buttons have 4 stages. These are Up, Over, Down and Hit. Now let us discuss these steps one by one. Up State: This is the stage when the cursor is away from the button. The appearance of a button when placed on the screen is the Up State. Over State: When the mouse cursor is placed over the button the appearance of the button can change.
This is referred as Over State Down State: Down State defines the appearance ofthe button when it is clicked. Hit Area: Hit area is the active part of the button. Your button may physically occupy a small area but if the Hit Area is big then' the active part of the button will also be large. Movie Clip symbols are also used to produce reusable pieces of animation. They have their own multi-frame and multi-layer timeline. This Timeline is not attached to the main Timeline of the scene. This Timeline may be thought of as a separate animation, which can be included within the main scene.
Movie Clips basically help to create an animation within another animation. Let's take an example to understand the use of a movie clip. Suppose you are trying to create a flying bird in Flash. Now if you consider the flying pattern you will definitely observe that basically there are two motions. One motion is the flapping of wings and the other is the movement of the whole body. So we can see in terms of animation that there is wing aniŽmation inside the flying animation. Now these two animations cannot be developed in the same scene. Here the concept of Movie Clip comes into play.
To create an an,imation of a flying bird first we have to create a Movie Clip where we will only show the flapping of wings. This Movie Clip tan be attached to the body in the main scene and the whole body along with the animated flapping wings can be put in to motion. The bird will then fly moving the wings, just as you see in your every day life. Movie Clip also helps us to play an animation within" a Loop. Agairi to create animated buttons these Movie clips instances can be put inside the Timeline of a Button symbol. The . Movie clips are scriptable with Action Script.