Algodoo

This is a simplified model of two of Saturns moons. When Red is closer, it goes faster, so it reaches up slowly towards Blue, which is farther away (please note, these are not the names of the actual moons) Red slowly reaches Blue, and slows Blue down, making it fall closer to the Green planet, and becausse of this, Red is given some of Blue's speed, enough to make it go farther away, and orbit slower, the ame thing happens, only with the places swapped, next orbit.