This bar chart displays the distribution of categorical grades (from “sehr gut” to “ungenügend”) with their absolute frequencies. Built with D3 v5, it uses scalable vector graphics (SVG) to render rectangular bars for each category, with axis scales defined via `d3.scaleLinear` and `d3.scaleBand`. The chart includes gridlines and value labels. Hovering over a bar triggers a smooth transition that enlarges the bar, increases its transparency, and displays the numeric difference between that bar and each other bar’s value.