anchor.diff:  
       function color(d) {
         if (d.root_node == true) {
  -        return "#94C8FF";
  +        return "#C2DEFC";
         }
         if (d.view_node == true) {
           return "#fd8d3c";
  
positive.code:         root;
  
      var force = d3.layout.force()
          .linkDistance(80)
          .charge(-120)
          .gravity(.05)
          .size([width, height])
          .on("tick", tick);
  
negative.code:       // Restart the force layout.
        force
            .nodes(nodes)
                    .linkDistance(200)
          .charge(-670)
          .gravity(.05)
  
                // .distance(100)
                // .charge(-670)
            .links(links)
            .start();
  
        // Update nodes.
        node = node.data(nodes, function(d) { return d.id; });
  