This example shows an interactive bar chart of letter frequencies from a CSV dataset. The visualization renders seven bars with rounded corners and gridlines, where clicking a bar highlights it and dims the others. Built with React and D3 v7, it uses `scaleBand` and `scaleLinear` for scales, `axisBottom` and `axisLeft` for axes, and a `ResizeObserver` in a custom `useDimensions` hook to handle responsive sizing. D3's data joins update the bars, with click handlers managing selection state through React's `useState`.