Gist101: a bunch of random circles

This is my first gist-bl.ock-ing attempt, let;s see how it goes...

<!DOCTYPE html>
<meta charset="utf-8">
<style>
rect {
  fill: none;
  pointer-events: all;
}

circle {
  fill: none;
  stroke-width: 2.5px;
}

</style>

var i = 0;

var svg = d3.select("#chart").append("svg")       // visualisation id 
    .attr("width", width)
    .attr("height", height);

svg.append("rect")
    .attr("width", width)
    .attr("height", height)
    .on("ontouchstart" in document ? "touchmove" : "mousemove", particle);

function particle() {
  var m = d3.mouse(this);

svg.insert("circle", "rect")
      .attr("cx", m[0])
      .attr("cy", m[1])
      .attr("r", 1e-6)
      .style("stroke", d3.hsl((i = (i + 1) % 360), 1, .5))
      .style("stroke-opacity", 1)
    .transition()
      .duration(4000)
      .ease(Math.sqrt)
      .attr("r", 400)
      .style("stroke-opacity", 1e-6)
      .remove();

d3.event.preventDefault();
}

</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js