:root {
  --bg-primary: #0b0f19;
  --bg-secondary: #111827;
  --bg-card: #1f2937;
  --bg-card-hover: #263345;
  --border-color: #374151;
  --border-accent: #059669;
  --text-main: #f3f4f6;
  --text-muted: #9ca3af;
  --text-dim: #6b7280;
  --accent-gold: #fbbf24;
  --accent-emerald: #10b981;
  --accent-blue: #38bdf8;
  --accent-rose: #f43f5e;
  --font-arabic: system-ui, -apple-system, "Segoe UI", Roboto, "Cairo", "Noto Sans Arabic", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
}

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

body {
  direction: rtl;
  text-align: right;
  font-family: var(--font-arabic);
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.7;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* LTR override for technical code, packet diagrams, and configs */
.ltr, code, pre, .mono, .packet-field, .command {
  direction: ltr;
  text-align: left;
  font-family: var(--font-mono);
}

a {
  color: var(--accent-blue);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--accent-gold);
}

.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Header & Nav */
header.site-header {
  background: rgba(17, 24, 39, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  padding: 16px 0;
}

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
}

.site-title {
  display: flex;
  align-items: center;
  gap: 12px;
}

.site-title h1 {
  font-size: 1.35rem;
  font-weight: 700;
  color: #fff;
}

.badge-version {
  background: rgba(16, 185, 129, 0.15);
  color: var(--accent-emerald);
  border: 1px solid rgba(16, 185, 129, 0.3);
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.8rem;
  font-weight: 600;
}

nav.main-nav ul {
  display: flex;
  list-style: none;
  gap: 20px;
}

nav.main-nav a {
  color: var(--text-muted);
  font-weight: 500;
  padding: 6px 12px;
  border-radius: 6px;
  transition: all 0.2s;
}

nav.main-nav a:hover, nav.main-nav a.active {
  color: #fff;
  background: var(--bg-card);
}

/* Hero Section */
.hero {
  padding: 60px 0 40px;
  border-bottom: 1px solid var(--border-color);
  background: radial-gradient(circle at 50% 0%, rgba(16, 185, 129, 0.08) 0%, transparent 70%);
}

.hero h2 {
  font-size: 2.2rem;
  font-weight: 800;
  margin-bottom: 16px;
  background: linear-gradient(135deg, #fff 0%, var(--accent-gold) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero p {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 850px;
  margin-bottom: 24px;
}

.meta-stats {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
  margin-top: 20px;
}

.stat-item {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 12px 20px;
  border-radius: 8px;
  min-width: 140px;
}

.stat-num {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--accent-emerald);
  font-family: var(--font-mono);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Grid & Cards */
.grid-units {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(360px, 1fr));
  gap: 24px;
  margin: 40px 0;
}

.unit-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 24px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s;
}

.unit-card:hover {
  transform: translateY(-3px);
  border-color: var(--accent-emerald);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.4);
}

.unit-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.unit-tag {
  font-size: 0.75rem;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 4px;
  background: rgba(56, 189, 248, 0.1);
  color: var(--accent-blue);
  border: 1px solid rgba(56, 189, 248, 0.2);
}

.unit-card h3 {
  font-size: 1.25rem;
  margin-bottom: 12px;
  color: #fff;
}

.unit-card p {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-bottom: 20px;
  flex-grow: 1;
}

.unit-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: 6px;
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  border: none;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--accent-emerald);
  color: #0b0f19;
}

.btn-primary:hover {
  background: #34d399;
  color: #0b0f19;
}

.btn-outline {
  background: transparent;
  color: var(--text-main);
  border: 1px solid var(--border-color);
}

.btn-outline:hover {
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

/* Lesson Content Styles */
.lesson-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 36px;
  margin: 40px 0;
}

@media (max-width: 1200px) {
  .lesson-layout {
    grid-template-columns: 1fr;
  }
}

.sidebar-nav {
  position: sticky;
  top: 90px;
  max-height: calc(100vh - 120px);
  overflow-y: auto;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 20px;
}

.sidebar-nav h4 {
  font-size: 0.95rem;
  text-transform: uppercase;
  color: var(--accent-gold);
  margin-bottom: 12px;
  letter-spacing: 0.5px;
}

.sidebar-nav ul {
  list-style: none;
}

.sidebar-nav li {
  margin-bottom: 8px;
}

.sidebar-nav a {
  display: block;
  padding: 6px 10px;
  border-radius: 4px;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.sidebar-nav a:hover, .sidebar-nav a.active {
  color: #fff;
  background: var(--bg-card);
}

.content-body h2 {
  font-size: 1.8rem;
  margin: 32px 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
  color: #fff;
}

.content-body h3 {
  font-size: 1.35rem;
  margin: 24px 0 12px;
  color: var(--accent-gold);
}

.content-body p {
  margin-bottom: 16px;
  color: #d1d5db;
}

/* Callout Blocks */
.callout {
  border-right: 4px solid var(--accent-blue);
  background: rgba(56, 189, 248, 0.05);
  padding: 16px 20px;
  border-radius: 0 8px 8px 0;
  margin: 24px 0;
}

.callout-warning {
  border-right-color: var(--accent-gold);
  background: rgba(251, 191, 36, 0.05);
}

.callout-danger {
  border-right-color: var(--accent-rose);
  background: rgba(244, 63, 94, 0.05);
}

.callout-success {
  border-right-color: var(--accent-emerald);
  background: rgba(16, 185, 129, 0.05);
}

.callout h4 {
  margin-bottom: 8px;
  color: #fff;
}

/* Code Blocks */
pre {
  background: #030712;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px 20px;
  overflow-x: auto;
  margin: 20px 0;
  font-size: 0.9rem;
  color: #38bdf8;
  line-height: 1.5;
}

/* Packet Table */
.packet-table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 0.9rem;
}

.packet-table th, .packet-table td {
  border: 1px solid var(--border-color);
  padding: 12px 14px;
  text-align: right;
}

.packet-table th {
  background: var(--bg-card);
  color: var(--accent-gold);
  font-weight: 700;
}

.packet-table tr:nth-child(even) {
  background: rgba(255, 255, 255, 0.02);
}

/* Interactive Timeline */
.timeline-container {
  position: relative;
  margin: 32px 0;
  padding-right: 24px;
  border-right: 2px solid var(--border-color);
}

.timeline-event {
  position: relative;
  margin-bottom: 28px;
}

.timeline-event::before {
  content: "";
  position: absolute;
  right: -31px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent-emerald);
  border: 2px solid var(--bg-primary);
}

.timeline-event.danger::before {
  background: var(--accent-rose);
}

.timeline-time {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent-gold);
  direction: ltr;
  display: inline-block;
  margin-bottom: 4px;
}

/* Navigation footer */
.lesson-nav-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 60px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
}

/* Footer */
footer.site-footer {
  border-top: 1px solid var(--border-color);
  background: var(--bg-secondary);
  padding: 32px 0;
  margin-top: 80px;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
}


/* =========================================================
   Mobile navigation controls — 2026-10-01
   UI-only: preserves all lesson/scientific content unchanged.
   ========================================================= */
.mobile-nav-toggle,
.sidebar-toggle {
  display: none;
}

@media (max-width: 1200px) {
  header.site-header {
    padding: 10px 0;
  }

  .header-inner {
    gap: 10px;
  }

  .site-title {
    flex: 1 1 auto;
    min-width: 0;
  }

  .site-title h1 {
    font-size: 1.12rem;
    white-space: nowrap;
  }

  .site-title .badge-version {
    font-size: 0.68rem;
    white-space: nowrap;
  }

  .mobile-nav-toggle,
  .sidebar-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-height: 42px;
    border: 1px solid var(--border-color);
    background: var(--bg-card);
    color: var(--text-main);
    border-radius: 8px;
    font: inherit;
    font-weight: 700;
    cursor: pointer;
  }

  .mobile-nav-toggle {
    width: 44px;
    flex: 0 0 44px;
    font-size: 1.3rem;
    line-height: 1;
  }

  nav.main-nav {
    display: none;
    flex: 1 0 100%;
    width: 100%;
  }

  nav.main-nav.is-open {
    display: block;
  }

  nav.main-nav ul {
    display: grid;
    grid-template-columns: 1fr;
    gap: 4px;
    width: 100%;
    padding-top: 8px;
  }

  nav.main-nav a {
    display: block;
    width: 100%;
    padding: 10px 12px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
  }

  .lesson-layout {
    margin-top: 18px;
    gap: 18px;
  }

  .sidebar-nav {
    position: static;
    top: auto;
    max-height: none;
    overflow: visible;
    padding: 10px;
  }

  .sidebar-toggle {
    width: 100%;
    min-height: 46px;
    background: var(--bg-card);
    color: var(--accent-gold);
  }

  .sidebar-nav:not(.is-open) > *:not(.sidebar-toggle) {
    display: none !important;
  }

  .sidebar-nav.is-open {
    max-height: min(70vh, 620px);
    overflow-y: auto;
  }

  .sidebar-nav.is-open .sidebar-toggle {
    position: sticky;
    top: 0;
    z-index: 2;
    margin-bottom: 12px;
  }

  .content-body h1 {
    font-size: 1.75rem !important;
  }

  .content-body h2 {
    font-size: 1.45rem;
  }

  .container {
    padding-left: 16px;
    padding-right: 16px;
  }
}

@media (max-width: 520px) {
  .site-title {
    gap: 7px;
  }

  .site-title h1 {
    font-size: 1rem;
  }

  .site-title .badge-version {
    padding: 2px 6px;
    font-size: 0.62rem;
  }
}