Fading/noisy-landscape, based on brownian motion, implemented in less than a tweet in a js1k environment:
d=a.getImageData(p=0,0,128,128);setInterval("for(i=k=66055;--i;d.data[p%k]++)p+=Math.random()*k*k&k;a.putImageData(d,0,0)",50)
Reload to watch again.