vec3 p,q=vec3(0,0,6),a,s=(FC.rgb*2.-r.xyx)/r.x;float w,d,i=0.;for(;i<80.;i++,q+=s*d)for(d=w=6.+t;w>t;w-=1.3){p=q;p.xz*=rotate2D(w);p.xy*=rotate2D(1.);for(a=abs(p);a.z<a.x||a.z<a.y;p=p.zxy,a=a.zxy);d=min(d,length(p.xz-vec2(p.y,1)*a.z/p.z)*.7-.07);}o.rgb=fw