/* Dark theme (default) */
    :root, [data-theme="dark"] {
      --bg: #0a1628;
      --card: #132337;
      --accent: #00d4ff;
      --accent2: #0a84ff;
      --text: #e8f1f8;
      --muted: #8ba3b8;
      --border: #1e3a5f;
      --header-bg: linear-gradient(180deg, #0d1f35 0%, #0a1628 100%);
      --card-h3: #ffffff;
      --shadow: rgba(0, 212, 255, 0.12);
      --toggle-bg: #1e3a5f;
      --toggle-icon: #00d4ff;
    }

    /* Light theme */
    [data-theme="light"] {
      --bg: #f0f4f8;
      --card: #ffffff;
      --accent: #0077b6;
      --accent2: #00a8e8;
      --text: #1a2a3a;
      --muted: #5a6a7a;
      --border: #d0d8e0;
      --header-bg: linear-gradient(180deg, #e8f0f8 0%, #f0f4f8 100%);
      --card-h3: #0a2540;
      --shadow: rgba(0, 119, 182, 0.15);
      --toggle-bg: #e0e8f0;
      --toggle-icon: #0077b6;
    }

    * { box-sizing: border-box; margin: 0; padding: 0; }

    body {
      font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
      background: var(--bg);
      color: var(--text);
      line-height: 1.5;
      min-height: 100vh;
      transition: background 0.3s ease, color 0.3s ease;
    }

    /* Theme toggle button */
    .theme-toggle {
      position: fixed;
      top: 1rem;
      right: 1rem;
      z-index: 100;
      width: 44px;
      height: 44px;
      border-radius: 50%;
      border: 1px solid var(--border);
      background: var(--toggle-bg);
      color: var(--toggle-icon);
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 1.25rem;
      transition: background 0.2s, transform 0.15s, border-color 0.2s;
      box-shadow: 0 2px 8px rgba(0,0,0,0.15);
    }
    .theme-toggle:hover {
      transform: scale(1.08);
      border-color: var(--accent);
    }
    .theme-toggle:focus {
      outline: 2px solid var(--accent);
      outline-offset: 2px;
    }
    .theme-toggle .sun { display: none; }
    .theme-toggle .moon { display: inline; }
    [data-theme="light"] .theme-toggle .sun { display: inline; }
    [data-theme="light"] .theme-toggle .moon { display: none; }

    header {
      background: var(--header-bg);
      border-bottom: 1px solid var(--border);
      padding: 1.5rem 1rem;
      text-align: center;
      transition: background 0.3s ease, border-color 0.3s ease;
    }

    .logo-wrap {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 0.75rem;
    }
    .logo-wrap img {
      max-width: 320px;
      width: 100%;
      height: auto;
      filter: drop-shadow(0 0 12px rgba(0, 212, 255, 0.35));
      transition: filter 0.3s ease;
    }
    [data-theme="light"] .logo-wrap img {
      filter: drop-shadow(0 2px 8px rgba(0, 119, 182, 0.2));
    }

    .tagline {
      color: var(--muted);
      font-size: 0.95rem;
      letter-spacing: 0.04em;
      transition: color 0.3s ease;
    }

    main {
      max-width: 1100px;
      margin: 0 auto;
      padding: 2rem 1rem 3rem;
    }

    h2 {
      font-size: 1.35rem;
      margin-bottom: 1rem;
      color: var(--accent);
      display: flex;
      align-items: center;
      gap: 0.5rem;
      transition: color 0.3s ease;
    }
    h2 .icon { font-size: 1.4rem; }

    section {
      margin-bottom: 2.5rem;
    }

    .grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
      gap: 1rem;
    }

    a.card {
      display: block;
      background: var(--card);
      border: 1px solid var(--border);
      border-radius: 12px;
      padding: 1.1rem 1.25rem;
      text-decoration: none;
      color: var(--text);
      transition: border-color 0.2s, transform 0.15s, box-shadow 0.2s, background 0.3s ease;
    }
    a.card:hover {
      border-color: var(--accent);
      transform: translateY(-3px);
      box-shadow: 0 8px 24px var(--shadow);
    }
    a.card h3 {
      font-size: 1.05rem;
      margin-bottom: 0.35rem;
      color: var(--card-h3);
      transition: color 0.3s ease;
    }
    a.card p {
      font-size: 0.85rem;
      color: var(--muted);
      transition: color 0.3s ease;
    }

    footer {
      text-align: center;
      padding: 1.5rem;
      color: var(--muted);
      font-size: 0.8rem;
      border-top: 1px solid var(--border);
      transition: color 0.3s ease, border-color 0.3s ease;
    }
    footer a { color: var(--accent); }

    @media (max-width: 480px) {
      .logo-wrap img { max-width: 240px; }
      h2 { font-size: 1.15rem; }
      .theme-toggle { top: 0.75rem; right: 0.75rem; width: 40px; height: 40px; }
    }