documents. Symbols can reduce the file size and download time for many animations. You can use a symbol countless times in a project, but Flash includes its data only once. Symbols are stored in the Library panel. When you drag a symbol to the Stage, Flash creates an instance of the symbol, leaving the original in the library. An instance is a copy of a symbol located on the Stage or nested inside another symbol There are three kinds of symbols in Flash, and each has advantages and limitations. You can tell whether a symbol is a graphic ( ), button ( ), or movie clip ( ) by looking at the icon next to it in the Library panel. Movie Clip Symbols Many designers use movie clip symbols for all kinds of objects in Flash because movie clips are the most flexible symbols. You can apply filters, color settings, and blending modes to a movie clip symbol. You can name each instance of a movie clip symbol, and control it with ActionScript. Movie clip Timelines are also the most flexible. They can contain sounds, interactive controls, and even other movie clip instances. Though they do not include the default frames for rollover states that are in a button symbol's Timeline, you can create a button using a movie clip symbol by using ActionScript to create the rollover states. Button Symbols You can quickly create interactive buttons with standard rollover states using button symbols. Unlike movie clip Timelines, button symbol Timelines have four frames: Up, Over, Down, and Hit. You can name individual button instances, and you can control them using ActionScript. You can also apply filters, blending modes, and color settings. * The Up state is the default state. * The Over state determines the button's appearance when the mouse rolls over it. * The Down state determines the button's appearance when it is clicked. * The Hit state defines the button's active area, which is the area that responds to the mouse click. Graphic Symbols Use graphic symbols for static images-that is, images you don't plan to animate-that are tied to the main Timeline. Graphic symbols are the least flexible symbols. They don't support ActionScript and, though you can animate a graphic symbol, interactive controls and sounds won't work. You also can't apply filters or blending modes to a graphic symbol.   Converting Objects to Symbols The interface layout you imported from Illustrator includes three green boxes, which will hold thumbnails for video clips. Before positioning the video clips on the boxes, you'll convert them to movie clip symbols, so that you could use ActionScript with them later. 1. In the Timeline, select frame 1 of the Preview Boxes layer to select the green boxes, which are the only objects on that layer. [View full size image] 2. Choose Modify > Convert to Symbol. 3. Name the symbol preview_boxes. 4. Select Movie Clip for the Type. 5. Click OK. The preview_boxes symbol appears in the library. Importing Bitmap Images