 vec2 opBlend( vec2 d1, vec2 d2, float k ) {
     return vec2(
       smin( d1.x, d2.x, k ),
-      smin( d1.y, d2.y, k )
+      d1.y // TODO: blend colors as well?
     );
 }
 


  pR(p.xy, 1.);
  p += vec3(.0, .0, a * .1);
  res = opU(res, vec2(sdBloodCell(opRep(p, vec3(3.))), 54.));

  pR(p.yz, 1.);
  p += vec3(.0, .0, a * .1);
  res = opU(res, vec2(sdBloodCell(opRep(p, vec3(3.))), 54.));

  return res;
}


  /* ---------- DEBUGGING ---------- */
  // Uncomment when debugging single scene
  // return scene0(pos);

  /* ---------- SCENES --------- */

