Websites/webkit.org/blog-files/content-security-policy/compass-base.css

.compass {
    --icon-length: 48px;
    --scaled-icon-length: calc(6 * var(--icon-length));
    height: var(--scaled-icon-length);
    width: var(--scaled-icon-length);
    background-color: blue;
    background-repeat: no-repeat;
    background-size: cover;
}