body {
      font-family: system-ui, sans-serif;
      display: flex;
      align-items: center;
      justify-content: center;
      height: 100vh;
      background: #f7f7f7;
      margin: 0;
    }
    .card {
      background: white;
      padding: 2rem;
      border-radius: 1rem;
      box-shadow: 0 4px 20px rgba(0,0,0,0.1);
      text-align: center;
      max-width: 400px;
    }
    h1 {
      margin-bottom: 0.5rem;
    }
    .date, .time {
      color: #666;
      font-size: 0.9rem;
    }
    #qrcode {
      margin: 2rem auto 0;
      display: flex;
      justify-content: center;
    }
    .error {
      text-align: center;
      font-size: 1.2rem;
      color: #b00;
    }