Selecting a Year on a Line Chart
This line chart shows population estimates and projections over time for global regions from 1950 to 2100. A vertical black line marks the currently selected year, which changes dynamically as the user moves the mouse across the chart. The visualization uses d3.line with curveBasis for smooth paths, d3.scaleTime and d3.scaleLinear for axes, and d3.mouse to detect hover position, triggering a re-render with the new year. Data comes from UN population estimates and medium-variant projections, rendered as SVG with a categorical color legend.