       units.append("svg:rect").
         style("stroke", "none").
         style("fill", "grey").
-        attr("x", 310).
+        attr("x", x_position).
         attr("y", (d,i) -> 350 + 20 * i).
         attr("height", (d) => @y d.value).
         attr("width", 40).
         style("opacity", 0.5)
 
       units.append("svg:text").
-        attr("x", 330).
+        attr("x", x_position + 20).
         attr("y", (d,i) -> 350 + 20 * i + 5).
         attr("text-anchor", "middle").
         text((d) -> "#{d.value}PJ")

      @links.data(@module.links.models, (d) -> d.cid).
        transition().duration(500).
        selectAll("text.link_label").
        attr("y", (link) => @y link.left_y()).
        text((d) => @format_value d.value())



  # Helper classes
  #
  Node: class extends Backbone.Model
    @width: 40
    @horizontal_spacing: 400

    initialize: =>
      # shortcut to access the collection objects
