body {
    font-family: Arial, sans-serif;
    background-color: #eef1f5;
    margin: 0;
    padding: 40px;
  }
  
  .usb-ui {
    max-width: 700px;
    margin: auto;
    background-color: white;
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0px 4px 12px rgba(0,0,0,0.1);
    text-align: center;
  }
  
  button {
    padding: 12px 24px;
    font-size: 16px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
  }
  
  button:hover {
    background-color: #0056b3;
  }
  
  #fileList {
    text-align: left;
    margin-top: 30px;
    padding: 0;
    list-style: none;
    border-top: 1px solid #ddd;
  }
  
  #fileList li {
    padding: 10px;
    border-bottom: 1px solid #eee;
    cursor: pointer;
  }
  
  #fileList li:hover {
    background-color: #f0f0f0;
  }
  
  #preview {
    margin-top: 30px;
    text-align: left;
    word-break: break-word;
  }
  
  #preview img {
    max-width: 100%;
    height: auto;
    margin-top: 10px;
  }
  
  #preview iframe {
    width: 100%;
    height: 500px;
  }