This example generates a full-screen grid of red vertical and horizontal bars, but uses an SVG `<mask>` to reveal only a circular region at the center of the canvas. A white rectangle inside the mask covers the entire viewport, while a black circle cuts out the visible area, clipping the bars to that shape. The code builds the SVG elements directly with `document.createElementNS` and uses the Google Fonts "Archivo" and "IBM Plex Sans" for styling. The result is a crisp, geometric pattern with a circular window.