Explain CSS image-set() for responsive graphics.

The image-set() function lets the browser choose the most appropriate image from a set of options based on the device's screen resolution and connection type.

Similar to the <picture> element in HTML, image-set() works inside CSS for background images. You can provide 1x, 2x, and 3x resolution assets, or different formats (like WebP vs JPEG), and the browser downloads only the optimal one.