Frame-by-frame animations -- the way cartoonists draw dozens of pictures, one for each frame -- are tedious work. Fortunately, Flash has an easier way to create animations: tweening. When you use tweening to animate an object, Flash interpolates the difference between keyframes and redraws the object on frames between keyframes to fill in the blanks, so to speak. When you play back the animation, there are no gaps, and smooth animation occurs.

There are two types of tweening animation: motion tweening, which interpolates changes in an object's position between keyframes; and shape tweening, which transforms an object's shape from one keyframe to the next.

To create a motion tween animation, follow these steps:

1. Create a shape in the first keyframe and then convert it into a symbol by pressing F8. Alternatively, select a symbol you've already created from the Library and drag it on Stage.

2. Determine how long the animation will be, advance to the final frame, and then insert a keyframe by pressing F6. The number of frames you'll need per second of animation is determined by the frame rate of your movie. If the frame rate is 12 fps, 36 frames equal 3 seconds of animation.

3. Change the object's position in the final keyframe. You use the Move tool to move the object to a different position. You can also change the position, size, and orientation of the object with the Free Transform tool.

4. Right-click (Windows) or Control-click (Macintosh) a frame between the keyframes that you just created, or right-click/Control-click the first keyframe in the animation, and then choose Create Motion Tween from the context menu. The background of the in-between frames is tinted a light blue with an arrow connecting the beginning and ending keyframes, indicating that you've successfully created a motion tween animation.

5. To preview the animation, click the Controller's Play button.