This line chart visualization displays population trends over time for various world regions. Users can hover over the chart to select a specific year, which triggers a vertical line to appear and updates the visualization accordingly. The chart is built using D3 v5, with the data sourced from UN population estimates. It employs D3’s `scaleTime`, `scaleLinear`, and `nest` functions to manage the time axis, population values, and multiple region groups, rendered as SVG paths.