This example demonstrates how to dynamically size an SVG element based on the bounding box of a text label. The page creates a single horizontal line with a centered text annotation, then draws a rounded rectangle behind the text using the dimensions returned by `getBBox()`. The SVG’s width is updated to fit the text plus padding. The code relies on native DOM methods like `createElementNS` and DOM APIs such as `setAttribute` and `getBBox`, with no external visualization libraries.