If you know the distance from the gravity sorce and calculate the new gravity from a certain distance.
if(planet gravity < stone gravity)
stone move more against the planet than the planet against the stone but they will collide if stone speed is to low around the planet.
if you put a gravity variable on the planet and a vector2. then putt a mass variable and a vector2 on the stone.
Then put a speed variable on the stone and calculate the G force to make the stone stay in orbit?
Anyone understand what my brain trying to do?