This example shows a horizontal bar chart of the top 20 most populous countries, with a hover interaction that highlights the selected bar in black and dims the others to gray. The chart is built using D3's `scaleBand` and `scaleLinear` to map country names and population values to positions, while `axisLeft` renders the y-axis. Mouseenter and mouseleave events on the bars update a `hoveredDatum` state to drive the color changes. The data comes from a CSV file containing country population figures, and the visualization uses an inner rectangle fill for visual separation.