This interactive bar chart displays the frequency of letters in a small dataset, rendered with React and D3. The visualization updates dynamically as users click bars to filter and highlight specific categories. Built with React 19 and D3 v7, the code leverages `d3.scaleBand`, `d3.scaleLinear`, `d3.axisBottom`, and `d3.axisLeft` to construct the chart. A `ResizeObserver` tracks container dimensions, while the `csv` API loads the sample data. The chart uses the `join` pattern for declarative SVG updates, with CSS transitions for smooth hover and selection effects.