[D3] Force + Drag + Zoom

HTML

<script src="http://d3js.org/d3.v3.min.js"></script>
<body>
    <div id="map"></div>
</body>

CSS

.node {
  font: 10px sans-serif;
}

.node-active{
  stroke: #555;
  stroke-width: 1.5px;
}

.link {
  stroke: #555;
  stroke-opacity: .3;
}

.link-active {
  stroke-opacity: 1;
}

.overlay {
  fill: none;
  pointer-events: all;
}

#map{
    border: 2px #555;
    width:1100px;
    height:400px;
}

div.tooltip {   
        position: absolute;                
        padding: 2px;                     
        background: white;   
        border-radius: 25px;
		padding: 20px; 
		border: 2px solid steelblue;
		opacity:1 !important;
    }
    
    
    .MakeItround{
	 border-radius: 50%;
}

JavaScript

var graph =...