(function() {
		'use strict'
    
			// SVG Setup //    
      var width = 500,
        height = 500,
      	margin = {top:50,bottom:50,left:50,right:50}
      
     	var svg = d3.select("#chart").append("svg")
        .attr("width", width + margin.right + margin.left)
        .attr("height", height + margin.left + margin.right)
        .append("g")
        .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")")  
        
      // Spiral Setup //
      var start = 0,
        end = 2.25,
        numSpirals = 8

      var theta = function(r) {
        return numSpirals * Math.PI * r
      };

      // used to assign nodes color by group
      var color = d3.scaleOrdinal(d3.schemeCategory10)

      var r = d3.min([width, height]) / 2 - 40

      var radius = d3.scaleLinear()
        .domain([start, end])
        .range([40, r])

      var points = d3.range(start, end + 0.001, (end - start) / 1000)

      var spiral = d3.radialLine()
        .curve(d3.curveCardinal)
        .angle(theta)
        .radius(radius)

      var path = svg.append("path")
        .datum(points)
        .attr("id", "spiral")
        .attr("d", spiral)
        .style("fill", "none")
        .style("stroke", "lightGray")

      // Circle Placement //
      var dot = svg.append("circle")
        .attr("class", "dot")
        .attr("fill", "#38d3fe")
        .attr("cx", path.node().getPointAtLength(0).x)
        .attr("cy", path.node().getPointAtLength(0).y)
        .attr("r", 8)

      // Time Scales and Animation //
      var spiralLength = path.node().getTotalLength()
      
      var timeScale = d3.scaleLinear()
      	.domain([0,60])
      	.range([0, spiralLength])
      
      function render(time){
        var l = timeScale(time)
          svg.selectAll(".dot")
            .attr("cx", path.node().getPointAtLength(l).x)
          	.attr("cy", path.node().getPointAtLength(l).y)
      }

      var p = 0
      
      function tick() {
        p = p + 0.015
        if (p > 60) { p = 0 }
        render(p)
      }

      d3.timer(tick)
		})()