Overlapping lines demonstrates a masking effect in SVG by layering horizontal and vertical bands. Horizontal rectangles are clipped using a circular SVG mask, creating a clean round boundary, while vertical rectangles extend full-height without masking, producing a checkered overlap. The code uses the SVG `mask` element, `circle`, and `rect` primitives, all generated programmatically with the Document Object Model (DOM) API. The scene fills the browser window via `createElementNS`, with static dimensions of 960 by viewport height, showing how simple shapes combine for visual contrast.