This example demonstrates a clean, interactive bar chart built with React and D3.js (v7). It visualizes a small dataset, showing the frequency of letters from a CSV file, with bars for each letter. The chart allows users to click on individual bars to highlight and dim others, creating a selection state. It is built by combining React's component model for state management and DOM control with D3's `scaleBand`, `scaleLinear`, `axisBottom`, and `axisLeft` APIs for rendering and layout. The visualization is fully responsive, using a `ResizeObserver` to recalculate dimensions.