Click & Drag a planet to move it

Press + or - or use the Mouse Wheel to zoom in or out

There's a level 2 in the editor with a larger planet and moon

You could change the parenting around to e.g. make planets get pulled back by the moons, or make the moons pull on each other, etc.

Obviously in space, planets and moons don't usually get this close without colliding, but this is just to show the concept