/* 扩展样式 */
.video-card { position: relative; }
.btn { display: inline-block; padding: 0.75rem 1.5rem; background: #3b82f6; color: white; border-radius: 6px; text-decoration: none; transition: background 0.3s; }
.btn:hover { background: #2563eb; text-decoration: none; }