ScrambledPhysics is a simple physics engine written in 100% native Processing. The aim of the project is to create a portable (within Processing) library which is good enough for basic physics simulations.
The example above should give you an idea of what it can do. This is simulating 100 charged particles (some positive, some negative), with an initial velocity of zero and a random placement within the universe, which is 640 x 480 pixels in size. When a particle reaches the edge, it wraps around.