This example shows GDP per capita for a selection of countries as a bar chart. Bars initially render in the order they appear in the data, with a transition animating their height on load. Users can hover over bars to highlight them in orange, and a checkbox below the chart sorts the bars in descending order by value. The visualization is built with React and D3 v4, using `d3.scaleBand`, `d3.scaleLinear`, `d3.axisBottom`, and `d3.axisLeft`, rendering to SVG with mouseover event handlers.