/* ── Design tokens (match index.css) ── */
    *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

    :root {
      --bg:         #0a0a0f;
      --surface:    #111118;
      --surface2:   #18181f;
      --border:     rgba(255,255,255,0.08);
      --border2:    rgba(255,255,255,0.14);
      --text:       #f0f0f5;
      --muted:      #888896;
      --accent:     #a5f3fc;
      --accent2:    #818cf8;
      --accent-dim: rgba(165,243,252,0.10);
      --radius-sm:  8px;
      --radius-md:  12px;
      --radius-lg:  18px;
      --font-sans:  'Outfit', system-ui, sans-serif;
      --font-mono:  'DM Mono', monospace;
      --font-display: 'Syne', system-ui, sans-serif;
      --nav-h: 60px;
    }
.lesson-mega-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--nav-h);
  background: rgba(0, 0, 0, 0.819);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border);
}
    html { scroll-behavior: smooth; }

    body {
      background: var(--bg);
      color: var(--text);
      font-family: var(--font-sans);
      font-size: 16px;
      line-height: 1.6;
      overflow-x: hidden;
    }

    a { color: inherit; text-decoration: none; }

    /* ── NAV ── */
    .nav {
      position: fixed;
      top: 0; left: 0; right: 0;
      z-index: 100;
      height: var(--nav-h);
      background: rgba(10,10,15,0.85);
      backdrop-filter: blur(18px);
      -webkit-backdrop-filter: blur(18px);
      border-bottom: 1px solid var(--border);
      display: flex;
      align-items: center;
    }

    .nav-inner {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 1.5rem;
      width: 100%;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 1rem;
    }

    .nav-logo {
      font-family: var(--font-display);
      font-size: 1.25rem;
      font-weight: 800;
      letter-spacing: 0.05em;
      flex-shrink: 0;
    }
    .nav-logo span { color: var(--accent); }

    .nav-links {
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }

    .nav-link {
      font-size: 0.875rem;
      font-weight: 500;
      color: var(--muted);
      padding: 0.35rem 0.8rem;
      border-radius: var(--radius-sm);
      transition: color 0.2s, background 0.2s;
    }
    .nav-link:hover, .nav-link.active {
      color: var(--text);
      background: var(--surface2);
    }
    .nav-link.active { color: var(--accent); }

    /* ── HERO ── */
    .blog-hero {
      padding: calc(var(--nav-h) + 5rem) 1.5rem 4rem;
      text-align: center;
      position: relative;
      overflow: hidden;
    }

    .blog-hero::before {
      content: '';
      position: absolute;
      inset: 0;
      background:
        radial-gradient(ellipse 60% 50% at 50% 20%, rgba(165,243,252,0.06) 0%, transparent 70%),
        radial-gradient(ellipse 40% 30% at 80% 80%, rgba(129,140,248,0.05) 0%, transparent 60%);
      pointer-events: none;
    }

    .blog-hero-badge {
      display: inline-block;
      font-family: var(--font-mono);
      font-size: 0.75rem;
      color: var(--accent);
      background: rgba(165,243,252,0.08);
      border: 1px solid rgba(165,243,252,0.25);
      border-radius: 999px;
      padding: 0.3rem 1rem;
      letter-spacing: 0.06em;
      margin-bottom: 1.5rem;
    }

    .blog-hero h1 {
      font-family: var(--font-display);
      font-size: clamp(2.2rem, 5vw, 3.5rem);
      font-weight: 800;
      line-height: 1.1;
      letter-spacing: -0.02em;
      margin-bottom: 1rem;
    }

    .blog-hero h1 em {
      font-style: normal;
      color: var(--accent);
    }

    .blog-hero-sub {
      font-size: 1rem;
      color: var(--muted);
      max-width: 520px;
      margin: 0 auto 2rem;
      line-height: 1.7;
    }

    /* ── CATEGORY FILTER ── */
    .categories {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 1.5rem 2.5rem;
      display: flex;
      align-items: center;
      gap: 0.5rem;
      flex-wrap: wrap;
    }

    .cat-btn {
      font-family: var(--font-mono);
      font-size: 0.75rem;
      font-weight: 500;
      letter-spacing: 0.04em;
      color: var(--muted);
      background: var(--surface);
      border: 1px solid var(--border2);
      border-radius: 999px;
      padding: 0.35rem 1rem;
      cursor: pointer;
      transition: color 0.2s, border-color 0.2s, background 0.2s;
    }

    .cat-btn:hover,
    .cat-btn.active {
      color: var(--accent);
      border-color: var(--accent);
      background: var(--accent-dim);
    }

    /* ── ARTICLES GRID ── */
    .blog-grid-wrap {
      max-width: 1280px;
      margin: 0 auto;
      padding: 0 1.5rem 6rem;
    }

    .blog-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
      gap: 1.5rem;
    }

    .blog-card {
      display: flex;
      flex-direction: column;
      gap: 0.75rem;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-lg);
      padding: 1.6rem;
      transition: border-color 0.25s, transform 0.2s, box-shadow 0.25s;
      position: relative;
      overflow: hidden;
    }

    .blog-card::before {
      content: '';
      position: absolute;
      top: 0; left: 0;
      width: 100%; height: 3px;
      background: var(--card-color, var(--accent));
      opacity: 0;
      transition: opacity 0.25s;
    }

    .blog-card:hover {
      border-color: var(--card-color, var(--accent));
      transform: translateY(-3px);
      box-shadow: 0 12px 40px rgba(0,0,0,0.35);
    }
    .blog-card:hover::before { opacity: 1; }

    .blog-card-meta {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      flex-wrap: wrap;
    }

    .blog-tag {
      font-family: var(--font-mono);
      font-size: 0.68rem;
      letter-spacing: 0.05em;
      color: var(--card-color, var(--accent));
      background: rgba(165,243,252,0.07);
      border: 1px solid rgba(165,243,252,0.18);
      border-radius: 999px;
      padding: 0.15rem 0.6rem;
    }

    .blog-date {
      font-family: var(--font-mono);
      font-size: 0.68rem;
      color: var(--muted);
    }

    .blog-card-title {
      font-family: var(--font-display);
      font-size: 1.1rem;
      font-weight: 700;
      line-height: 1.35;
      color: var(--text);
      transition: color 0.2s;
    }

    .blog-card:hover .blog-card-title { color: var(--accent); }

    .blog-card-excerpt {
      font-size: 0.875rem;
      color: var(--muted);
      line-height: 1.6;
      flex: 1;
    }

    .blog-card-footer {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding-top: 0.75rem;
      border-top: 1px solid var(--border);
      margin-top: auto;
    }

    .blog-read-time {
      font-family: var(--font-mono);
      font-size: 0.72rem;
      color: var(--muted);
    }

    .blog-arrow {
      font-size: 0.875rem;
      font-weight: 600;
      color: var(--card-color, var(--accent));
      display: flex;
      align-items: center;
      gap: 0.3rem;
      transition: gap 0.2s;
    }
    .blog-card:hover .blog-arrow { gap: 0.55rem; }

    /* ── FOOTER ── */
    .footer {
      background: #0d0d12;
      border-top: 1px solid var(--border);
      padding: 2.5rem 1.5rem;
      text-align: center;
    }

    .footer-links {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 1.5rem;
      flex-wrap: wrap;
      margin-bottom: 1rem;
    }

    .footer-links a {
      font-size: 0.85rem;
      color: var(--muted);
      transition: color 0.2s;
    }
    .footer-links a:hover { color: var(--accent); }

    .footer-copy {
      font-family: var(--font-mono);
      font-size: 0.72rem;
      color: var(--muted);
      letter-spacing: 0.04em;
    }

    /* ── RESPONSIVE ── */
    @media (max-width: 600px) {
      .nav-links { display: none; }
      .blog-grid { grid-template-columns: 1fr; }
    }
  

    .mega-nav,
.lesson-mega-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--nav-h);
  background: rgba(0, 0, 0, 0.819);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border-bottom: 1px solid var(--border);
}
.mega-nav .nav-container,
.lesson-mega-nav .nav-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.mega-nav .nav-logo,
.lesson-mega-nav .nav-logo {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 800;
  letter-spacing: 0.05em;
  color: var(--text);
}

.mega-nav .nav-logo span,
.lesson-mega-nav .nav-logo span {
  color: var(--accent);
}

.mega-nav .nav-links,
.lesson-mega-nav .nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.mega-nav .nav-links a,
.lesson-mega-nav .nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--muted);
  transition: color 0.2s;
  padding: 0.5rem 0;
}

.mega-nav .nav-links a:hover,
.lesson-mega-nav .nav-links a:hover,
.mega-nav .nav-links a.active,
.lesson-mega-nav .nav-links a.active {
  color: var(--text);
}

/* Search toggle button in nav */
.mega-nav .search-toggle,
.lesson-mega-nav .search-toggle {
  background: none;
  border: 1px solid var(--border2);
  border-radius: var(--radius-sm);
  color: var(--muted);
  cursor: pointer;
  padding: 0.45rem 0.55rem;
  display: flex;
  align-items: center;
  transition: color 0.2s, border-color 0.2s, background 0.2s;
}

.mega-nav .search-toggle:hover,
.lesson-mega-nav .search-toggle:hover {
  color: var(--text);
  border-color: var(--accent);
  background: var(--accent-dim);
}
.lesson-nav-container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 1.5rem;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.btn-signin {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--bg);
  background: var(--accent);
  border: none;
  border-radius: var(--radius-sm);
  padding: 0.45rem 1.1rem;
  cursor: pointer;
  transition: opacity 0.2s;
}

.btn-signin:hover { opacity: 0.88; }


.hamburger-btn {
  display: none;
  background: none;
  border: 1px solid var(--border2);
  border-radius: var(--radius-sm);
  color: var(--muted);
  cursor: pointer;
  padding: 0.45rem 0.55rem;
  align-items: center;
  transition: color 0.2s, border-color 0.2s, background 0.2s;
}

.hamburger-btn:hover {
  color: var(--text);
  border-color: var(--accent);
  background: var(--accent-dim);
}

@media (max-width: 768px) {
  .hamburger-btn { display: flex; }
}


/* Search button */
.search-btn {
  background: none;
  border: 1px solid var(--border2);
  border-radius: var(--radius-sm);
  color: var(--muted);
  cursor: pointer;
  padding: 0.45rem 0.55rem;
  display: flex;
  align-items: center;
  transition: color 0.2s, border-color 0.2s, background 0.2s;
}

.search-btn:hover {
  color: var(--text);
  border-color: var(--accent);
  background: var(--accent-dim);
}