This interactive bar chart, built with React and D3 v7, visualizes the frequency distribution of letters from a CSV dataset. Clicking a bar toggles its highlight, dimming unselected bars to focus attention on specific categories. The chart uses `scaleBand` and `scaleLinear` for positioning and includes gridlines from `axisLeft`. A `ResizeObserver` in `useDimensions` tracks container size, and React renders while D3 handles SVG elements through selections and the data join pattern.