This example demonstrates a simple SVG visualization where 100 horizontal rectangles are drawn across the full window width, with a circular mask revealing only the central portion of the stacked bars. The code uses d3.select, d3.range, and the .join() method to bind data to rectangle elements, then appends an SVG mask containing a black background rect and a white circle to create the viewport effect. Rendering is handled entirely through SVG attributes, with the visualization sized dynamically to the browser window.