This stylized bar chart displays the top 10 most populous countries using data from the United Nations World Population Prospects 2019. Built with React and D3 v5, it renders SVG rectangles whose widths are scaled by population via `scaleLinear`, while `scaleBand` positions each country along the y-axis. The chart includes styled axes, tick marks, and a tooltip on each bar, with the D3 `format` function converting large numbers to abbreviations like "B" for billions.