Algodoo

Although tidally locked to Jupiter (always facing it with the same side, like our moon) Io experiences enormous tidal forces because of the eccentricity of it´s orbit. These forces raise the ground up to 300m and are the cause of geological acitivity that makes Io the most vulcanicly active object in our solar system with 120-150 active volcanos.
Pressing "i" you can observe the elliptical deformation of Io when getting closer to Jupiter during a revolution. (Of cource nothing is to scale or we wouldn´t see much of it. Io´s trajectory is far more "circle"-shaped in reality as well.)