This example presents a dropdown-driven bar chart comparing height and weight percentages across geographic blocks. Users select a metric from the dropdown, triggering a smooth 1-second transition that updates bar heights, fill colors, and the y-axis scale. The visualization uses D3 v5 with d3.scaleBand and d3.scaleLinear for positioning, a sequential color scale for encoding values, and transition methods for animated updates. Data comes from a local CSV file, rendered as SVG rectangles with tooltips that display block names and values on hover.