This visualization is a bar chart displaying the frequency of letters (A through G) from a simple CSV data file. The chart shows each letter as a rounded bar, with a clean layout, axis labels, and gridlines. Built with React and D3.js v7, it uses D3's `scaleBand`, `scaleLinear`, `axisBottom`, and `axisLeft` to construct the scales and axes. The bars change color and opacity upon click to highlight a selected letter, and the SVG rendering updates dynamically based on container dimensions.