The script is based on Matthew Shieh's Fire demo and Giles Thomas's Learning WebGL: Some particle effects. (Canvas is matched to the browser window).
300 sprite particles with random speeds, colors and lifetimes are moved up and to the center. Colors are faded with time. After a particle "death" it is initialized randomly at the bottom. Particles are scaled to 1/5 of the viewport size.

WebGL Demos     updated 4 July 2010