Press the green flag twice before making each new orbit. Input values for the different variables and watch as your orbit is drawn(The speed of the planet is not accurate). The yellow dot represents the body you planet is orbiting. The red arrow shows what direction the planet wants to go but cannot due to the gravitation pull of the body it orbits around. Press space to see what would happen if the body your planet is orbiting around were to disappear.
Bruno is my hero.