From the Author:
Particle experiment all computed from GPU. No loops used on CPU. Use 2 texture framebuffers, one for velocity and other for position, and vertex texture lookups to move particles around. This tecnique are well documented on this paper http://www.2ld.de/gdc2004/MegaParticlesPaper.pdf.
You can add more particles changin the particle parameter on the url (always power of 2).