skeleton.html

<!DOCTYPE html>
<html>
<head>
  <style>
    html, body { margin: 0; padding: 0; height: 100%; background: transparent; display: flex; justify-content: center; align-items: center; }
    
    .skeleton { 
      background: #e0e0e0; 
      animation: pulse 1.5s infinite; 
      border-radius: 8px;
      opacity: 0.7;
    }
    
    .banner { 
      width: calc(min(100vw - 45px, 841px)); 
      height: auto; 
      max-height: 512px;
      aspect-ratio: 16/9;
    }
    
    @keyframes pulse { 0% { opacity: 0.6; } 100% { opacity: 0.9; } }
  </style>
</head>
<body>
  <script>
    const skeleton = document.createElement('div');
    skeleton.className = 'skeleton banner';
    document.body.appendChild(skeleton);
  </script>
</body>
</html>