d3 change circles

HTML

<script src="http://d3js.org/d3.v3.js"></script>
  <svg id="svg" width="360" height="180">
    <circle class="little" cx="180" cy="45" r="12"></circle>
    <circle class="little" cx="60" cy="90" r="12"></circle>
    <circle class="little" cx="300" cy="135" r="12"></circle>
  </svg>

CSS

svg circle {
    fill: grey;
    stroke: black;
}

JavaScript

var svg = d3.select("#svg")
  .on("click", function() {
    var circle = svg.selectAll("circle");
    circle.style("fill", "steelblue");
    circle.attr("cy", 90);
    circle.attr("r", 30);
});