This bar chart visualizes the popularity of programming languages using data from Stack Overflow’s 2019 survey. Hovering over a bar highlights it and displays the percentage difference between the hovered language’s value and every other language’s value, with a dashed reference line marking the selected baseline. The visualization uses D3.js v5 with SVG rendering, employing `d3.scaleBand` and `d3.scaleLinear` for axes, and `d3.axisLeft`/`d3.axisBottom` for gridlines and ticks. Interactive transitions via `d3.transition()` animate opacity changes on mouseenter and mouseleave events.