Source for demo by Oscar Nevarez Leal.
var a=0.9,g,k="canvas",l=document,m=Math;k=l.createElement(k);l.getElementsByTagName("body")[0].appendChild(k);s=6;k.height=300;k.width=k.height;W=k.width;H=k.height;
g=function(h,i,b,c,e,f,j){if(j<=0)(function(n,o){a=(a+0.01)%1;with(k.getContext("2d")){globalAlpha=a;fillStyle="#"+m.round(16777215*m.random()).toString(16);fillRect(n,o,s,s)}})(h+(b+e)/2,i+(c+f)/2);else{g(h,i,e/2,f/2,b/2,c/2,j-1);g(h+b/2,i+c/2,b/2,c/2,e/2,f/2,j-1);g(h+b/2+e/2,i+c/2+f/2,b/2,c/2,e/2,f/2,j-1);g(h+b/2+e,i+c/2+f,-e/2,-f/2,-b/2,-c/2,j-1)}};d=function(){g(0,0,W,0,0,H,s)};setInterval("d()",1E3);