Allows an optional corner-rounding parameter in the polygon() CSS shape function. Developers can specify a length value to round polygon corners without manually computing bezier curves. Interactive demo: https://codepen.io/yisi/pen/NPRLEQN CSSWG issue: https://github.com/w3c/csswg-drafts/issues/9843
Rounded polygons are a common design pattern on the web. Without this feature, developers who want rounded corners on a polygon shape must manually compute bezier control points or use workarounds such as SVG clip paths. The polygon() round parameter makes this directly expressible in CSS, reducing complexity and improving maintainability.