Learning Circles

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    .container {
      width: 800px;
      margin: 0 auto;
      border: 1px solid #666666;
      padding: 50px 0;
      
    }
    .mine {
      width: 500px;
      height: 400px; 
      background-color: #eee;
      margin: 0 auto;
      display: block;
    }
  </style>
</head>

<body>
  <div class="container">
    <svg class="mine"></svg>
  </div>
  <script>
    // Feel free to change or delete any of the code you see in this editor!
    var svg = d3.select("svg");
    //var w = svg.width;

svg.append("text")
      .attr("y", 100)
      .attr("x", 50)
      .attr("font-size", 24)
      .attr("font-family", "Georgia")
    	.style("opacity", 0)
    	.text("Some text");
    
    svg.append("circle")
    	.attr("r", 50)
    	.attr("cx", 250)
    	.attr("cy", 200)
    	.attr("fill", "#507799");
    
    d3.selectAll("text").transition().delay(3000).style("opacity",1);
    d3.selectAll("circle").transition().duration(2000).attr("cy",300);
    d3.selectAll("circle").transition().duration(1000).attr("cy",100);

</script>
</body>

https://d3js.org/d3.v4.min.js