function Line () {
  Module.call(this, 'line', 'Drawing lines. Tween expects something in the `$&$>>$&$` format.')

  this.ports.step = new Port(this, 'step', false, true, 0, 100, 'The tween line index.')
  this.ports.thickness = new Port(this, 'thickness', true, true, 1, 100, 'The tween line thickness.')

  this.methods.stroke = new Method('stroke', 'x1,y1&x2,y2', 'Stroke positions.', function (q) {
    ronin.line.stroke_multi(q)
  })

  this.methods.tween = new Method('tween', 'tween:$&$>>$&$ step->thickness', 'Stroke lines between strokes.', function (q) {
    var from = q.from
    var to = q.to

    ronin.line.ports.step.write(0)
    while (ronin.line.ports.step.value < ronin.line.ports.step.max) {
      var progress = ronin.line.ports.step.value / parseFloat(ronin.line.ports.step.max)
      var new_positions = tween_positions(from, to, progress)
      ronin.line.stroke_multi(new_positions)
      ronin.line.ports.step.write(ronin.line.ports.step.value + 1)
    }
  })

  this.preview = function (q) {
    // TODO
    // console.log(q);
  }

  this.stroke_multi = function (coordinates) {
    var from = coordinates[0]
    for (pos_id in coordinates) {
      var pos = coordinates[pos_id]
      ronin.line.stroke(from, pos)
      from = pos
    }
  }

  this.stroke = function (from, to, ctx = ronin.cursor.target.context()) {
    ctx.beginPath()
    ctx.globalCompositeOperation = 'source-over'
    ctx.moveTo((from.x * 2), (from.y * 2))
    ctx.lineTo((to.x * 2), (to.y * 2))
    ctx.lineCap = 'round'
    ctx.lineWidth = clamp(ronin.line.ports.thickness.value, 1, 200) * 0.1
    ctx.strokeStyle = '#000'
    ctx.stroke()
    ctx.closePath()
  }

  function clamp (v, min, max) {
    return v < min ? min : v > max ? max : v
  }

  function tween_positions (froms, tos, progress) {
    var a = []
    for (pos_id in froms) {
      var from = froms[pos_id]
      var to = tos[pos_id]
      a.push(tween_position(from, to, progress))
    }

    return a
  }

  function tween_position (from, to, progress) {
    var offset = { x: to.x - from.x, y: to.y - from.y }
    return { x: from.x + offset.x * progress, y: from.y + offset.y * progress }
  }
}