Multitouch by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1,maximum-scale=1">
<style>

html,
body {
  height: 100%;
}

body {
  margin: 0;
}

svg {
  display: block;
  overflow: hidden;
  width: 100%;
  height: 100%;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var color = d3.scale.category10();

var svg = d3.select("body").append("svg")
    .attr("width", innerWidth)
    .attr("height", innerHeight);

var circle = svg.selectAll("circle.touch");

d3.select("body")
    .on("touchstart", touch)
    .on("touchmove", touch)
    .on("touchend", touch);

function touch() {
  d3.event.preventDefault();

  circle = circle
      .data(d3.touches(svg.node()), function(d) { return d.identifier; });

  circle.exit()
      .attr("class", null)
    .transition()
      .attr("r", 1e-6)
      .remove();

  circle.enter().append("circle")
      .attr("class", "touch")
      .attr("r", 1e-6)
      .style("fill", function(d) { return color(d.identifier); })
    .transition()
      .duration(500)
      .ease("elastic")
      .attr("r", 48);

  circle
      .attr("cx", function(d) { return d[0]; })
      .attr("cy", function(d) { return d[1]; });
}

</script>