This demo simulates the Sun-Earth-Moon-Apollo System and traces the paths of Earth, Moon and Apollo. Note the cycloid/loop-the-loop movements of the Moon and Apollo. a-z keys puts pen up-down for Apollo and traces its path. Up-Down arrows puts pen up-down for the moon and traces its path. Left-Right arrows puts pen up-down for the Earthand traces its path. Space bar clears the traces. h key hides the Sun, Earth, Moon and Apollo s key shows the Sun, Earth, Moon and Apollo
