* {
    box-sizing: border-box;
}

b {
    margin: 0 0.3em;
}

/**
 * Aspect ratio
 * Example: <div style="--custom-aspect-ratio=16/9">...</div>
 */
[style*="--custom-aspect-ratio"] > :first-child {
    width: 100%;
}
[style*="--custom-aspect-ratio"] > img {
    height: auto;
}
@supports (--custom: property) {
    [style*="--custom-aspect-ratio"] {
        position: relative;
    }
    [style*="--custom-aspect-ratio"]::before {
        content: "";
        display: block;
        padding-bottom: calc(100% / (var(--custom-aspect-ratio)));
    }
    [style*="--custom-aspect-ratio"] > :first-child {
        position: absolute;
        top: 0;
        left: 0;
        height: 100%;
    }
}