Animation is the movement, or change, of objects through time. Animation can be as simple as moving a box across the Stage from one frame to the next. It can also be much more complex. As you’ll see in this lesson, you can animate many different aspects of a single object. You can change an object’s position on the Stage, change its color or transparency, change its size or rotation, or animate the special filters that you saw in the previous lesson. You also have control over an object’s path of motion, and even its easing, which is the way an object accelerates or decelerates.
In Flash, the basic workflow for animation goes like this: Select an object on the Stage, right-click/Ctrl-click, and choose Create Motion Tween. Move the red playhead to a different point in time and move the object to a new position or change one of its properties. Flash takes care of the rest.
Motion tweens create animation for changes in position on the Stage and for changes in size, color, or other attributes. Motion tweens require you to use a symbol instance. If the object you’ve selected is not a symbol instance, Flash will automatically ask to convert the selection to a symbol.
Flash also automatically separates motion tweens on their own layers, which are called Tween layers. There can be only one motion tween per layer without any other element in the layer. Tween layers allow you to change various attributes of your instance at different key points over time. For example, a spaceship could be on the left side of the Stage at the beginning keyframe and at the far-right side of the Stage at an ending keyframe, and the resulting tween would make the spaceship fly across the Stage.
The term “tween” comes from the world of classic animation. Senior animators would be responsible for drawing the beginning and ending poses for their characters. The beginning and ending poses were the keyframes of the animation. Junior animators would then come in and draw the “in-between” frames, or do the “in-betweening.” Hence, “tweening” refers to the smooth transitions between keyframes.