This example demonstrates how SVG masks and primitive shapes combine to create a striking visual effect. It displays 100 horizontal rectangles filling the viewport, with a circular mask revealing only the area inside a 200-pixel-radius circle centered on the screen. Using D3.js version 7.6.1, the code binds data via `d3.range` and `selectAll` to generate the rectangles, then appends a `mask` element containing a black background rectangle and a white circle to control visibility. The rendering approach relies entirely on SVG elements and DOM manipulation through `d3.select`.