body {
      display: flex;
      justify-content: center;
      align-items: center;
      margin: 0;
    }
    .container {
      background-color: white;
      padding: 30px;
      border-radius: 12px;
      box-shadow: 0 4px 12px rgba(0,0,0,0.1);
      width: 100%;
      max-width: 420px;
      text-align: center;
    }
    h1 { color: #1d1d1f; margin-bottom: 25px; font-size: 24px; }
    select, input { width: 100%; padding: 12px; margin-bottom: 15px; border: 1px solid #ddd; border-radius: 8px; font-size: 16px; }
    button { width: 100%; padding: 14px; border: none; background-color: #007aff; color: white; border-radius: 8px; font-weight: 600; cursor: pointer; }
    button:hover { background-color: #005ecb; }
    #qrcode { margin: 20px auto; width: 256px; height: 256px; }
    #downloadBtn { background-color: #34c759; display: none; }
    #downloadBtn:hover { background-color: #2ca348; }
    .input-group { display: none; }