Easing

One thing I want to clear up right off the bat is that there is more than one type of easing. Even in the Flash IDE, while you're making a motion tween, you have the ability to "ease in" or "ease out." The type of easing I will be discussing here is the same as the "ease out" of a motion tween. A bit later in this chapter, in the "Advanced easing" section, I'll provide you with a link where you can find out how to do all kinds of easing.

Simple easing

Simple easing is a very basic concept. You have something over here and you want to move it over there. Since you're creating the "illusion of motion," you want to move it there gradually, over several frames. You could simply find the angle between the two, set a speed, use some trigonometry to work out the vx and vy, and set it in motion. Then you could check the distance to the target on each frame (using the Pythagorean Theorem, as described in Chapter 3), and when it was there, stop it. That approach might actually be adequate in some situations, but if you're trying to make something look like it's moving naturally, it won't do.