Wahahahaha! Finally the swarming works as it did all those years ago when I first made it in Cortex Command! Unfortunately, the particles tend to clump together because they are now rotating around the mouse, and not the average of their positions.
Using the raw power of Processing, I have constructed a basic Platforming engine, complete with Terrain (the Scenery AND the actual terrain were drawn Paint). It also has support for holes, which you can use drag around using the mouse. Player is WASD.