SVG Fundamentals
Four overlaid rounded rectangles demonstrate core SVG fundamentals within a D3.js v5 environment. The visualization shows two overlapping shapes with varying corner radii, positioned using both pixel and viewport-height units. One red and one green rectangle dominate the center, while a pair of small vertical bars in red and green sit offset to the right, each with distinct dimensions. The code explicitly defines the SVG canvas, `rect` elements, and fill attributes, while a separate script imports D3’s `select` function and a local module to display a text message.