css5

p:nth-of-type(2) {
    background: #fdebd0;
    padding: 5px;
}

p:nth-last-of-type(1) {
    background: #d5f5e3;
    padding: 5px;
}

li:nth-child(3n+1) {
    background: #e8f4fd;
    padding: 5px;
}

li:nth-last-child(2n+1) {
    background: #fef3c7;
    padding: 5px;
}

li:only-child {
    color: #16a34a;
    font-weight: bold;
}

input:default {
    box-shadow: 0 0 0 2px #3498db;
}

input:enabled {
    border: 2px solid #2ecc71;
}

input:read-only {
    background: #f8f9fa;
    border: 1px dashed #95a5a6;
}

input:read-write {
    border: 2px solid #3498db;
}

input:placeholder-shown {
    border-color: #95a5a6;
    background: #f8f9fa;
}

custom-element:defined {
    border: 2px solid #2ecc71;
    padding: 10px;
}

.fullscreen-demo:fullscreen {
    background: #2c3e66;
    color: white;
}

video:picture-in-picture {
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

:host {
    display: block;
    background: #f8f9fa;
    border-radius: 8px;
    padding: 10px;
}

::slotted(p) {
    color: #3498db;
    font-weight: bold;
}

div:empty {
    background: #fdebd0;
    border: 2px dashed #e74c3c;
    padding: 20px;
}

textarea:blank {
    border: 2px solid #e74c3c;
}

section:target {
    background: #f9e79f;
    border-left: 4px solid #f1c40f;
}

div:target-within {
    background: #d5f5e3;
    border-left: 4px solid #2ecc71;
}

a:any-link {
    text-decoration: none;
    font-weight: bold;
}

dialog:modal {
    border: none;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}

.popover:popover-open {
    animation: fadeIn 0.3s ease;
    border: none;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}

:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
}

.parent :scope {
    border-left: 3px solid #3498db;
    padding-left: 10px;
}

p:lang(fr) {
    quotes: "«" "»";
}
p:lang(en) {
    quotes: "“" "”";
}