The goal is to move a rectangle from top left to bottom right with an animation, changing the colour. The rectangle is placed in the upper left corner of the stage and a keyframe is defined at 0.
This specifies the starting point of the animation. At second 3, a second keyframe is created. The state of the rectangle is adjusted in the second keyframe by positioning it in the bottom right corner and setting the color to red.
The Composer automatically calculates the animation between the created keyframes. That is, the rectangle automatically moves from the upper-left to the bottom-right corner of the stage and, while doing so, continuously changes color from blue to red. The animation can be played on stage or in the preview by selecting the play button (triangle symbol).