This example demonstrates a simple masking effect in SVG, where a set of horizontal stripes is revealed only through a circular window at the center of the viewport. The visualization uses plain SVG elements created dynamically via the `document.createElementNS` method. A white rectangle serves as the mask base, while a black circle defines the transparent region, and the stripes are drawn as individual `rect` elements with the mask applied. The code runs without any external libraries, relying purely on native browser APIs and JavaScript.