<style>
    body {
      font-family: Arial, sans-serif;
      margin: 0;
      background: #0f172a;
      color: #f8fafc;
    }

    header {
      padding: 24px 8%;
      border-bottom: 1px solid #1e293b;
    }

    main {
      padding: 40px 8%;
      max-width: 900px;
    }

    input, button {
      padding: 12px;
      margin: 6px 0;
      width: 100%;
      max-width: 360px;
      box-sizing: border-box;
    }

    button {
      cursor: pointer;
      background: #2563eb;
      color: white;
      border: none;
      border-radius: 6px;
    }

    .card {
      background: #111827;
      border: 1px solid #334155;
      border-radius: 12px;
      padding: 20px;
      margin-bottom: 16px;
    }

    .muted {
      color: #94a3b8;
    }

    .hidden {
      display: none;
    }
  </style>