This is a cleaned and simplified version of the core simulation / animation used in the Inventory Management section of the Stitch Fix Algorithms Tour.
The figure was drawn in a visual svg editor (based on a napkin sketch of the system) and the svg file was then copied into the html and cleaned up a bit. The dynamic elements are tagged with ids or classes for selection and manipulation within a d3.timer loop. Their line widths or rectangle heights are based on the timestep values of a dynamic system simulation which is also carried out within the d3.timer loop.