function render(t){
  var intersections = allIntersections(lines)

  lines.forEach(function(d){ d.count = 0 })
  intersections.forEach(function(i){
    i.lines[0].count++, i.lines[1].count++ })
  intersections.forEach(function(i){
    i.count = Math.max(i.lines[0].count, i.lines[1].count) })

  ctx.fillStyle = 'rgba(0, 0, 0, .01)'
  ctx.fillRect(0, 0, width, height)

  ctx.beginPath()
  lines.forEach(function(d){
    ctx.moveTo(d[0][0],    d[0][1])
    ctx.lineTo(d[1][0],    d[1][1])
  })
  ctx.strokeStyle = 'rgba(0,0,0,.1)'
  ctx.lineWidth = 1
  ctx.stroke()

  intersections.forEach(function(i){  
    ctx.fillStyle = '#fff'
    ctx.fillStyle = color(i.count)

    var r = 1.5
    ctx.beginPath()
    ctx.moveTo(i[0] + r, i[1])
    ctx.arc(i[0], i[1], r, 0, 2 * Math.PI)
    ctx.fill()
  })

}
render()

if (window.timer) timer.stop()
window.timer = d3.timer(function(t){
  points.forEach(function(d){
    var s = 1
    d[0] += d.dx*s
    d[1] += d.dy*s
    if (d[0] < 0 && d.dx < 0 || d[0] > width  && d.dx > 0) d.dx = -d.dx
    if (d[1] < 0 && d.dy < 0 || d[1] > height && d.dy > 0) d.dy = -d.dy
  })

  render(t)
})