Google Gravity Tornado -

The simulation often uses a JavaScript port of the Box2D physics engine. This library calculates how objects collide, spin, and react to force, allowing the elements to move realistically rather than just following a pre-set animation. Why People Love Interactive Web Experiments

Once the page loads, move your mouse cursor across the screen. The movement of your mouse often acts as the "thermal core" of the tornado, drawing the spinning components toward your pointer. google gravity tornado