animateMotion
A linear animateMotion from left to right is superposed
by a linear animate for cy (circle) from top to bottom.
animateMotion has several keyPoints and keyTimes.
The duration of the animations is 30s.
The visible effect is
a motion along the given gray path.
If the red center of the circle becomes visible, an error
occured. Note, that the velocity is enlarged with every
keyTime.