void mainImage(out vec4 o, vec2 F){
    vec2 R = iResolution.xy; 
    o-=o;
    for(float d,t = iTime*.1, i = 0. ; i > -1.; i -= .06 )          	
    {   d = fract( i -3.*t );                                          	
        vec4 c = vec4( ( F - R *.5 ) / R.y *d ,i,0 ) * 28.;            	
        for (int j=0 ; j++ <27; )                                      	
            c.xzyw = abs( c / dot(c,c)                                 	
                    -vec4( 7.-.2*sin(t) , 6.3 , .7 , 1.-cos(t/.8))/7.);	
       o -= c * c.yzww  * d--*d  / vec4(3,5,1,1);                     
    }
}