This webpage is an HTML5/js simple particle system simulation with configurable charged particles (attractive or repulsive) and a bunch of other particles reacting to them in a no-border universe. Charged particles can react to other charged particles if you set their position to "free".
You can change (from top to bottom) : charge of mouse-added charged particle, number and positions of charged particles, their charge value, neutral particles maximum speed and negative exponent of distance in force calculation.
Notice how remarkable is their behavior with such simple rule, and how similar to images of the univers at large scale (galaxies or planets orbiting a star) or at subatomic scale they move.