This interactive line chart displays population trends over time by region, using data from UN population estimates. A vertical black line marks the currently selected year, and users can hover over the chart to update this selection, which the visualization updates in real time. The D3 code organizes regions by color using `d3.scaleOrdinal` and `d3.schemeCategory10`, draws the lines with `d3.line` and `d3.curveBasis`, and renders axes with `d3.axisLeft` and `d3.axisBottom`. A custom legend component maps colors to region names, and the data is loaded from CSV files.