A proportional symbols map visualizes transportation costs across US states, with larger circles representing higher expenses. Hovering a symbol highlights it and displays a tooltip with the exact state name and cost. The visualization uses D3 v3 with topojson for state boundaries and pre-computed state centroids from a JSON file, while CSV data supplies the cost values. Circle size is scaled linearly, and the top ten most expensive states are colored distinctly. The map animates opacity transitions on hover and applies a dark theme.