This interactive bar chart displays the number of COVID-19 cases for the top 20 countries, using a horizontal bar mark with length encoding the case count. Built with React and D3 v5, the visualization renders as SVG and uses `scaleBand` for the categorical y-axis, `scaleLinear` for the quantitative x-axis, and `d3.csv` to load the data from a GitHub-hosted CSV file. The code explicitly draws axis ticks and gridlines, while `ReactDOM.render` mounts the chart into the DOM, and the title "Corona Cases" is provided in the HTML.