.node_link .node > circle {
  fill: #dddddd;
  stroke: #777777;
  stroke-width: 2px;
}

.node_link .node > text {
  font-family: sans-serif;
  text-anchor: middle;
  pointer-events: none;
  
  -webkit-touch-callout: none; /* iOS Safari */
  -webkit-user-select: none;   /* Chrome/Safari/Opera */
  -khtml-user-select: none;    /* Konqueror */
  -moz-user-select: none;      /* Firefox */
  -ms-user-select: none;       /* IE/Edge */
  user-select: none;           /* non-prefixed version, currently
                                  not supported by any browser */
}

.node_link .link {
  stroke: teal;
  stroke-width: 4px;
  opacity: 0.6;
}
.node_link .directed.link {
  stroke: orange;
  marker-end: url(#end-arrow);
}
.node_link #end-arrow {
  fill: orange;
}
.node_link .selected.link {
  opacity: 1;
}
.node_link .unselected.link {
  opacity: 0.2;
}