:root {
      font-family: system-ui, -apple-system, Segoe UI, Roboto, "Helvetica Neue", Arial;
    }

    body {
      margin: 0;
      background: #f7fafc;
      color: #0f172a;
      display: flex;
      flex-direction: column;
      align-items: center;
      min-height: 100vh;
    }

    /* ---------- Navbar ---------- */
    nav {
      width: 100%;
      background: #0ea5a4;
      color: white;
      padding: 12px 24px;
      box-sizing: border-box;
      display: flex;
      align-items: center;
      justify-content: center;
      position: relative;
      box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    }

    .nav-brand {
      position: absolute;
      left: 24px;
      font-weight: 700;
      font-size: 18px;
      color: white;
      text-decoration: none;
    }

    nav ul {
      list-style: none;
      display: flex;
      gap: 24px;
      margin: 0;
      padding: 0;
    }

    nav a {
      color: white;
      text-decoration: none;
      font-weight: 500;
    }

    nav a:hover {
      text-decoration: underline;
    }

    /* ---------- Main Container ---------- */
    .app {
      width: 980px;
      max-width: 95%;
      background: #fff;
      border-radius: 12px;
      box-shadow: 0 8px 30px rgba(2, 6, 23, 0.08);
      padding: 24px;
      box-sizing: border-box;
      margin-top: 32px;
    }

    h1 {
      margin: 0 0 8px;
      font-size: 20px;
    }

    p.lead {
      margin: 0 0 20px;
      color: #475569;
    }

    .row {
      display: flex;
      gap: 12px;
      flex-wrap: wrap;
    }

    .card {
      flex: 1 1 320px;
      background: #f8fafc;
      border: 1px solid #e6eef6;
      padding: 12px;
      border-radius: 8px;
    }

    input[type="file"] {
      display: block;
      margin-bottom: 8px;
    }

    button {
      background: #0ea5a4;
      color: white;
      border: none;
      padding: 8px 12px;
      border-radius: 6px;
      cursor: pointer;
    }

    button.secondary {
      background: #64748b;
    }

    .info {
      font-size: 13px;
      color: #334155;
      margin-top: 8px;
    }

    .result {
      margin-top: 12px;
      padding: 12px;
      background: #eef2ff;
      border-radius: 8px;
      border: 1px solid #e6e9ff;
    }

    a.download {
      display: inline-block;
      margin-top: 4px;
    }

    .small {
      font-size: 13px;
      color: #475569;
    }

    .ads-placeholder {
      height: 90px;
      background: linear-gradient(90deg, #f1f5f9, #fff);
      border: 1px dashed #cbd5e1;
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      margin-top: 12px;
      color: #94a3b8;
    }

    pre {
      white-space: pre-wrap;
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, "Roboto Mono", monospace;
      font-size: 12px;
      margin: 0;
      max-height: 220px;
      overflow: auto;
    }

    .footer {
      margin-top: 18px;
      font-size: 13px;
      color: #64748b;
    }