Once you have a shape tween, you can obtain finer control
over the look of the morph, by adding shape hints. You put the time indicator
on a keyframe in the shape-tween layer, and then choose Modify>Shape>Add
Shape Hint:
Now it is possible to move the little red circle with
an "a" to the lower left arc of the larger circle. This is the
source point
which on the red square we move up to the top edge. In
interactive building language this means: morph the shape in such a way
as to move the point designated by the red "a" to the position
of the green "a".
