.content-placeholder:empty {
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: loading 1.5s infinite;
    height: 100px;
    border-radius: 4px;
    position: relative;
}
.content-placeholder:empty::before {
    content: "Loading content...";
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #666;
    font-style: italic;
}
@keyframes loading {
    0% { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}
.content-placeholder:not(:empty) {
    background: #fff;
    border: 1px solid #ddd;
    padding: 20px;
    border-radius: 4px;
}
.toggle-btn {
    background: #007bff;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 4px;
    cursor: pointer;
    margin-bottom: 10px;
}
.toggle-btn:hover {
    background: #0056b3;
}