Animation is what Flash is all about. Sure, Flash offers tons of drawing and special-effect tools, but these are all means to an end: a series of slightly different drawings that you can string together to create the illusion of movement.
In the old days, animators had to create each drawing, or frame , by handa daunting process when you consider that your average feature presentation clicks by at 24 frames per second. (That's 1,440 drawings per minute of onscreen animation. Expensive? Hoo boy.)
To keep those costs down, animation companies did what all self-respecting companies do: They figured out how to separate the highly skilled labor from the less-skilled labor. They figured out that there are key drawings (called keyframes ) that show big changes in the finished animation, and a certain number of less-detailed, in-between drawings (regular frames) they could assign to lower-paid workers. For example, say you're a producer working on an animation showing a cartoon kangaroo jumping up into the air. If you get a skilled animator to draw the kangaroo-on-the-ground, kangaroo-midway, and kangaroo-at-the-top frames, you can hand these keyframes off to a low-paid tweener. All the tweener has to do is copy the keyframes and make a few adjustments, and bingo: You've got yourself a finished animation at a bargain- basement price.
Flash, like the animation studios of old, gives you the opportunity to use tweening to slash the time it takes to produce a finished animation. In this chapter, you see both approaches: frame-by-frame (still the best choice when you need to create highly complex, tightly controlled animations) and tweening (wherein Flash serves as your very own low-paid illustrator).