Here is a planet with a moon and some orbiting spaceships. Simple gravity calculations affect the paths of the orbiting things. The spaceships point themselves in their direction of travel. You can click and drag things to new positions, but their velocities stay the same. When the orbiting things cross over, the alpha of the upper sprite changes (it decreases until the alpha value wraps).
The spaceship and planet images were rendered with Povray. I made the spaceship, but the planet was a modification of an example scene that came with Povray. The stars and moon are images I had lying around on my computer.
Here is the code for this Project