This bar chart displays the distribution of CSS color specifications across different levels, counting how many colors exist for each level. The visualization uses D3.js v7 to load a CSV file via `d3.csv`, aggregate the data with `d3.rollup`, and render an SVG bar chart using `d3.scaleBand` and `d3.scaleLinear`. Bars are drawn as SVG rectangles that turn orange on hover, with axes generated by `d3.axisBottom` and `d3.axisLeft`. The x-axis labels are rotated for readability, and the y-axis shows the number of colors per level.