 
   move: (e) ->
     markWidth = parseInt(@element.style.width, 10)
+
+    # no overlapping of marks
     leftXPos = Math.max (@toCanvasXPoint(e) - @pointerOffset), (@closestXBelow || 0)
     leftXPos = Math.min leftXPos, ((@closestXAbove || @canvas.width) - markWidth)
 

      e.preventDefault()
      @mark = new Mark(e, @)
      @marks.create(@mark)
      @mark.onMouseDown(e)
      @mark.dragging = true
      @mark.draw(e)

  plotPoints: (xMin = @smallestX, xMax = @largestX) ->
    @xMin = xMin

    @element.style.textAlign = 'center'

    @startingPoint = @toCanvasXPoint(e) - @minWidth()

    @dragging = true

    @element.addEventListener 'mousemove', @updateCursor
    @element.addEventListener 'mousedown', @onMouseDown
