/* ============================================================
   Mobile Data Systems & Connectivity Basics Guide
   Main Stylesheet — Deep Blue + Gray + White Theme
   ============================================================ */

/* --- Google Fonts Import --- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

/* --- CSS Variables --- */
:root {
  --blue-900: #0a1628;
  --blue-800: #0d2240;
  --blue-700: #0f2d57;
  --blue-600: #1a3f73;
  --blue-500: #1e52a0;
  --blue-400: #2563c4;
  --blue-300: #4a86e8;
  --blue-200: #93bbf5;
  --blue-100: #dbeafe;
  --blue-50:  #eff6ff;

  --gray-900: #111827;
  --gray-800: #1f2937;
  --gray-700: #374151;
  --gray-600: #4b5563;
  --gray-500: #6b7280;
  --gray-400: #9ca3af;
  --gray-300: #d1d5db;
  --gray-200: #e5e7eb;
  --gray-100: #f3f4f6;
  --gray-50:  #f9fafb;

  --white: #ffffff;
  --accent-cyan: #06b6d4;
  --accent-teal: #0d9488;
  --accent-amber: #f59e0b;

  --font-main: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Courier New', monospace;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.15), 0 2px 4px rgba(0,0,0,0.08);
  --shadow-lg: 0 10px 30px rgba(0,0,0,0.18), 0 4px 8px rgba(0,0,0,0.10);
  --shadow-xl: 0 20px 50px rgba(0,0,0,0.22);

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --transition: all 0.25s ease;
  --max-width: 1200px;
}

/* --- Reset & Base --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-main);
  background-color: var(--gray-50);
  color: var(--gray-800);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--blue-500);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  color: var(--blue-400);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol {
  list-style: none;
}

/* ============================================================
   LAYOUT UTILITIES
   ============================================================ */

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.container--narrow {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 80px 0;
}

.section--alt {
  background-color: var(--white);
}

.section--dark {
  background-color: var(--blue-900);
  color: var(--white);
}

.section--blue {
  background-color: var(--blue-800);
  color: var(--white);
}

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: start;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.flex {
  display: flex;
  align-items: center;
}

.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.text-center { text-align: center; }
.text-left   { text-align: left; }

/* ============================================================
   TYPOGRAPHY
   ============================================================ */

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-main);
  font-weight: 700;
  line-height: 1.25;
  color: var(--blue-900);
  letter-spacing: -0.02em;
}

h1 { font-size: clamp(2rem, 4vw, 3rem); }
h2 { font-size: clamp(1.6rem, 3vw, 2.25rem); }
h3 { font-size: clamp(1.25rem, 2vw, 1.6rem); }
h4 { font-size: 1.2rem; }
h5 { font-size: 1.05rem; }

p {
  margin-bottom: 1.25rem;
  color: var(--gray-700);
  font-size: 1rem;
  line-height: 1.8;
}

p:last-child { margin-bottom: 0; }

.lead {
  font-size: 1.2rem;
  color: var(--gray-600);
  font-weight: 400;
  line-height: 1.75;
  max-width: 720px;
}

.section-label {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--blue-400);
  background: var(--blue-50);
  border: 1px solid var(--blue-200);
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 16px;
}

.section-label--light {
  color: var(--blue-200);
  background: rgba(255,255,255,0.08);
  border-color: rgba(255,255,255,0.15);
}

/* --- Dark Background Text Fixes --- */
.section--dark h1,
.section--dark h2,
.section--dark h3,
.section--dark h4,
.section--blue h1,
.section--blue h2,
.section--blue h3,
.section--blue h4 {
  color: var(--white);
}

.section--dark p,
.section--blue p {
  color: var(--blue-100);
}

.section--dark .lead,
.section--blue .lead {
  color: var(--blue-200);
}

/* ============================================================
   NAVIGATION
   ============================================================ */

.navbar {
  background-color: var(--blue-900);
  border-bottom: 1px solid var(--blue-800);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 20px rgba(0,0,0,0.3);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
  padding: 0 24px;
  max-width: var(--max-width);
  margin: 0 auto;
}

.navbar__logo {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.navbar__logo-icon {
  width: 38px;
  height: 38px;
  background: linear-gradient(135deg, var(--blue-400), var(--accent-cyan));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.navbar__logo-icon svg {
  width: 22px;
  height: 22px;
  fill: white;
}

.navbar__logo-text {
  display: flex;
  flex-direction: column;
}

.navbar__logo-name {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--white);
  line-height: 1.2;
  letter-spacing: -0.01em;
}

.navbar__logo-sub {
  font-size: 0.68rem;
  font-family: var(--font-mono);
  color: var(--blue-300);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.navbar__nav {
  display: flex;
  align-items: center;
  gap: 4px;
}

.navbar__nav a {
  color: var(--blue-200);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 8px 14px;
  border-radius: var(--radius-md);
  transition: var(--transition);
  white-space: nowrap;
}

.navbar__nav a:hover,
.navbar__nav a.active {
  color: var(--white);
  background: rgba(255,255,255,0.1);
}

.navbar__nav .dropdown {
  position: relative;
}

.navbar__nav .dropdown-menu {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  background: var(--blue-800);
  border: 1px solid var(--blue-700);
  border-radius: var(--radius-lg);
  padding: 8px;
  min-width: 220px;
  box-shadow: var(--shadow-lg);
}

.navbar__nav .dropdown:hover .dropdown-menu {
  display: block;
}

.navbar__nav .dropdown-menu a {
  display: block;
  padding: 10px 14px;
  color: var(--blue-200);
  font-size: 0.85rem;
  border-radius: var(--radius-md);
}

.navbar__nav .dropdown-menu a:hover {
  color: var(--white);
  background: rgba(255,255,255,0.08);
}

.navbar__cta {
  background: linear-gradient(135deg, var(--blue-500), var(--blue-400));
  color: var(--white) !important;
  padding: 9px 18px !important;
  border-radius: var(--radius-md) !important;
  font-weight: 600 !important;
  box-shadow: 0 2px 8px rgba(37,99,196,0.35);
}

.navbar__cta:hover {
  background: linear-gradient(135deg, var(--blue-400), var(--blue-300)) !important;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(37,99,196,0.45) !important;
}

/* Mobile Menu Toggle */
.navbar__toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 8px;
  background: none;
  border: none;
}

.navbar__toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--white);
  border-radius: 2px;
  transition: var(--transition);
}

/* ============================================================
   HERO SECTIONS
   ============================================================ */

.hero {
  background: linear-gradient(160deg, var(--blue-900) 0%, var(--blue-800) 50%, var(--blue-700) 100%);
  padding: 90px 0 80px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle at 20% 50%, rgba(37,99,196,0.15) 0%, transparent 50%),
    radial-gradient(circle at 80% 20%, rgba(6,182,212,0.1) 0%, transparent 40%);
  pointer-events: none;
}

/* Grid overlay */
.hero::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 60px 60px;
  pointer-events: none;
}

.hero__content {
  position: relative;
  z-index: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.hero h1 {
  color: var(--white);
  margin-bottom: 20px;
  max-width: 780px;
}

.hero .lead {
  color: var(--blue-200);
  margin-bottom: 36px;
  max-width: 640px;
}

.hero__meta {
  display: flex;
  align-items: center;
  gap: 24px;
  margin-top: 40px;
  flex-wrap: wrap;
}

.hero__stat {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 20px;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: var(--radius-lg);
}

.hero__stat-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--blue-500), var(--accent-cyan));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
}

.hero__stat-icon svg {
  width: 18px;
  height: 18px;
  fill: white;
}

.hero__stat-text strong {
  display: block;
  color: var(--white);
  font-size: 0.9rem;
  font-weight: 600;
}

.hero__stat-text span {
  font-size: 0.75rem;
  color: var(--blue-300);
}

/* Page Hero (inner pages) */
.page-hero {
  background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-700) 100%);
  padding: 60px 0 50px;
  position: relative;
  overflow: hidden;
}

.page-hero::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 50px 50px;
  pointer-events: none;
}

.page-hero__content {
  position: relative;
  z-index: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.page-hero h1 {
  color: var(--white);
  margin-bottom: 14px;
}

.page-hero .lead {
  color: var(--blue-200);
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 20px;
  font-size: 0.82rem;
  font-family: var(--font-mono);
}

.breadcrumb a {
  color: var(--blue-300);
}

.breadcrumb a:hover {
  color: var(--white);
}

.breadcrumb span {
  color: var(--blue-500);
}

.breadcrumb .current {
  color: var(--blue-200);
}

/* ============================================================
   BUTTONS / CTAs
   ============================================================ */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-main);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 12px 24px;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  border: none;
  text-decoration: none;
  white-space: nowrap;
}

.btn svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.btn--primary {
  background: linear-gradient(135deg, var(--blue-500), var(--blue-400));
  color: var(--white);
  box-shadow: 0 4px 14px rgba(37,99,196,0.4);
}

.btn--primary:hover {
  background: linear-gradient(135deg, var(--blue-400), var(--blue-300));
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(37,99,196,0.5);
  color: var(--white);
}

.btn--outline {
  background: transparent;
  color: var(--white);
  border: 1.5px solid rgba(255,255,255,0.35);
  padding: 11px 24px;
}

.btn--outline:hover {
  background: rgba(255,255,255,0.1);
  border-color: rgba(255,255,255,0.6);
  color: var(--white);
  transform: translateY(-2px);
}

.btn--outline-blue {
  background: transparent;
  color: var(--blue-500);
  border: 1.5px solid var(--blue-300);
}

.btn--outline-blue:hover {
  background: var(--blue-50);
  border-color: var(--blue-500);
  color: var(--blue-600);
}

.btn--lg {
  font-size: 1rem;
  padding: 15px 32px;
}

.btn-group {
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}

/* ============================================================
   CARDS
   ============================================================ */

.card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-xl);
  padding: 32px;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
  border-color: var(--blue-200);
}

.card--featured {
  border-color: var(--blue-300);
  background: linear-gradient(160deg, var(--blue-50) 0%, var(--white) 100%);
}

.card__icon {
  width: 52px;
  height: 52px;
  background: linear-gradient(135deg, var(--blue-500), var(--blue-400));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  box-shadow: 0 4px 12px rgba(37,99,196,0.3);
}

.card__icon svg {
  width: 26px;
  height: 26px;
  fill: white;
}

.card__icon--cyan {
  background: linear-gradient(135deg, var(--accent-cyan), var(--accent-teal));
  box-shadow: 0 4px 12px rgba(6,182,212,0.3);
}

.card__icon--amber {
  background: linear-gradient(135deg, var(--accent-amber), #d97706);
  box-shadow: 0 4px 12px rgba(245,158,11,0.3);
}

.card h3 {
  margin-bottom: 12px;
  font-size: 1.15rem;
}

.card p {
  font-size: 0.925rem;
  color: var(--gray-600);
  margin-bottom: 0;
}

.card__badge {
  position: absolute;
  top: 16px;
  right: 16px;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--blue-100);
  color: var(--blue-600);
  border: 1px solid var(--blue-200);
}

.card__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 20px;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--blue-500);
}

.card__link svg {
  width: 14px;
  height: 14px;
  transition: transform 0.2s;
}

.card__link:hover svg {
  transform: translateX(4px);
}

/* ============================================================
   DIAGRAM COMPONENTS
   ============================================================ */

.diagram {
  background: var(--blue-900);
  border: 1px solid var(--blue-700);
  border-radius: var(--radius-xl);
  padding: 40px;
  margin: 40px 0;
  position: relative;
  overflow: hidden;
}

.diagram::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
}

.diagram__title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--blue-300);
  margin-bottom: 32px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.diagram__title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--blue-700);
}

/* Flow Diagram */
.flow {
  display: flex;
  align-items: center;
  gap: 0;
  position: relative;
  z-index: 1;
  flex-wrap: wrap;
  justify-content: center;
}

.flow__node {
  background: var(--blue-800);
  border: 1.5px solid var(--blue-600);
  border-radius: var(--radius-lg);
  padding: 18px 24px;
  text-align: center;
  min-width: 130px;
  transition: var(--transition);
}

.flow__node:hover {
  border-color: var(--blue-400);
  background: var(--blue-700);
}

.flow__node-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--blue-500), var(--accent-cyan));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 10px;
}

.flow__node-icon svg {
  width: 20px;
  height: 20px;
  fill: white;
}

.flow__node-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--white);
  line-height: 1.3;
}

.flow__node-sub {
  font-size: 0.68rem;
  color: var(--blue-300);
  font-family: var(--font-mono);
  margin-top: 4px;
}

.flow__arrow {
  display: flex;
  align-items: center;
  padding: 0 8px;
  color: var(--blue-400);
}

.flow__arrow svg {
  width: 20px;
  height: 20px;
  fill: var(--blue-400);
}

/* Architecture Diagram */
.arch-diagram {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  position: relative;
  z-index: 1;
}

.arch-layer {
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--blue-700);
  border-radius: var(--radius-lg);
  padding: 20px;
}

.arch-layer__title {
  font-size: 0.72rem;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent-cyan);
  margin-bottom: 16px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--blue-700);
}

.arch-layer__items {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.arch-item {
  background: var(--blue-800);
  border: 1px solid var(--blue-600);
  border-radius: var(--radius-md);
  padding: 10px 14px;
  font-size: 0.8rem;
  color: var(--blue-100);
  display: flex;
  align-items: center;
  gap: 8px;
}

.arch-item::before {
  content: '';
  width: 6px;
  height: 6px;
  background: var(--blue-400);
  border-radius: 50%;
  flex-shrink: 0;
}

/* Data Bar Visual */
.data-bar {
  background: var(--blue-800);
  border-radius: var(--radius-md);
  overflow: hidden;
  height: 8px;
  margin-bottom: 8px;
}

.data-bar__fill {
  height: 100%;
  background: linear-gradient(90deg, var(--blue-400), var(--accent-cyan));
  border-radius: var(--radius-md);
  transition: width 1s ease;
}

/* ============================================================
   SECTION HEADERS
   ============================================================ */

.section-header {
  margin-bottom: 56px;
}

.section-header--center {
  text-align: center;
}

.section-header--center .lead {
  margin: 0 auto;
}

.section-header h2 {
  margin-bottom: 16px;
}

/* ============================================================
   FEATURE BLOCKS
   ============================================================ */

.feature-block {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
  padding: 60px 0;
  border-top: 1px solid var(--gray-200);
}

.feature-block:first-child {
  border-top: none;
}

.feature-block--reverse .feature-block__visual {
  order: -1;
}

.feature-block__text h3 {
  margin-bottom: 16px;
  font-size: 1.5rem;
}

.feature-block__text .lead {
  font-size: 1rem;
  margin-bottom: 24px;
}

.feature-block__list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 24px;
}

.feature-block__list li {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  font-size: 0.925rem;
  color: var(--gray-700);
}

.feature-block__list li::before {
  content: '';
  width: 20px;
  height: 20px;
  background: linear-gradient(135deg, var(--blue-500), var(--blue-400));
  border-radius: 50%;
  flex-shrink: 0;
  margin-top: 2px;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 20 20' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M7 10l2 2 4-4' stroke='white' stroke-width='2' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-color: var(--blue-500);
  background-size: contain;
}

.feature-block__visual {
  background: var(--blue-900);
  border: 1px solid var(--blue-700);
  border-radius: var(--radius-xl);
  padding: 32px;
  position: relative;
  overflow: hidden;
  min-height: 280px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.feature-block__visual::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.025) 1px, transparent 1px);
  background-size: 30px 30px;
  pointer-events: none;
}

/* ============================================================
   STATS ROW
   ============================================================ */

.stats-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--gray-200);
  border-radius: var(--radius-xl);
  overflow: hidden;
  border: 1px solid var(--gray-200);
}

.stat-item {
  background: var(--white);
  padding: 32px 24px;
  text-align: center;
}

.stat-item__value {
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--blue-600);
  line-height: 1;
  margin-bottom: 8px;
  letter-spacing: -0.03em;
}

.stat-item__label {
  font-size: 0.82rem;
  color: var(--gray-500);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

/* ============================================================
   INFO BOXES
   ============================================================ */

.info-box {
  background: var(--blue-50);
  border: 1px solid var(--blue-200);
  border-left: 4px solid var(--blue-500);
  border-radius: var(--radius-md);
  padding: 20px 24px;
  margin: 28px 0;
}

.info-box--note {
  background: #fef3c7;
  border-color: var(--accent-amber);
  border-left-color: var(--accent-amber);
}

.info-box--tip {
  background: #ecfdf5;
  border-color: #6ee7b7;
  border-left-color: var(--accent-teal);
}

.info-box__title {
  font-size: 0.82rem;
  font-family: var(--font-mono);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--blue-600);
  margin-bottom: 8px;
}

.info-box--note .info-box__title { color: #92400e; }
.info-box--tip .info-box__title  { color: #065f46; }

.info-box p {
  font-size: 0.9rem;
  color: var(--gray-700);
  margin-bottom: 0;
}

/* ============================================================
   TABLE OF CONTENTS
   ============================================================ */

.toc {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-xl);
  padding: 28px 32px;
  margin-bottom: 40px;
}

.toc__title {
  font-size: 0.82rem;
  font-family: var(--font-mono);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--gray-500);
  margin-bottom: 16px;
}

.toc__list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 32px;
}

.toc__list li {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.875rem;
}

.toc__list a {
  color: var(--blue-600);
  font-weight: 500;
}

.toc__list a:hover {
  color: var(--blue-400);
}

.toc__num {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--gray-400);
  min-width: 20px;
}

/* ============================================================
   BLOG CARDS
   ============================================================ */

.blog-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-xl);
  overflow: hidden;
  transition: var(--transition);
}

.blog-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
  border-color: var(--blue-200);
}

.blog-card__image {
  height: 200px;
  background: linear-gradient(135deg, var(--blue-800), var(--blue-600));
  position: relative;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

.blog-card__image-icon {
  width: 64px;
  height: 64px;
  background: rgba(255,255,255,0.1);
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
}

.blog-card__image-icon svg {
  width: 32px;
  height: 32px;
  fill: rgba(255,255,255,0.7);
}

.blog-card__image::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.04) 1px, transparent 1px);
  background-size: 30px 30px;
}

.blog-card__body {
  padding: 28px;
}

.blog-card__tag {
  font-size: 0.72rem;
  font-family: var(--font-mono);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--blue-500);
  margin-bottom: 12px;
}

.blog-card h3 {
  font-size: 1.1rem;
  margin-bottom: 12px;
  line-height: 1.4;
}

.blog-card h3 a {
  color: var(--blue-900);
}

.blog-card h3 a:hover {
  color: var(--blue-500);
}

.blog-card p {
  font-size: 0.875rem;
  color: var(--gray-600);
  margin-bottom: 20px;
}

.blog-card__meta {
  display: flex;
  align-items: center;
  gap: 16px;
  font-size: 0.78rem;
  color: var(--gray-400);
  border-top: 1px solid var(--gray-100);
  padding-top: 16px;
}

/* ============================================================
   SPEC TABLE
   ============================================================ */

.spec-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  margin: 24px 0;
}

.spec-table th {
  background: var(--blue-900);
  color: var(--white);
  padding: 14px 20px;
  text-align: left;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.spec-table th:first-child { border-radius: var(--radius-md) 0 0 0; }
.spec-table th:last-child  { border-radius: 0 var(--radius-md) 0 0; }

.spec-table td {
  padding: 14px 20px;
  border-bottom: 1px solid var(--gray-200);
  color: var(--gray-700);
  vertical-align: top;
}

.spec-table tr:last-child td { border-bottom: none; }

.spec-table tr:nth-child(even) td {
  background: var(--gray-50);
}

.spec-table .tag {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 20px;
  font-size: 0.72rem;
  font-weight: 600;
  font-family: var(--font-mono);
}

.tag--blue   { background: var(--blue-100); color: var(--blue-700); }
.tag--green  { background: #dcfce7; color: #15803d; }
.tag--amber  { background: #fef3c7; color: #92400e; }
.tag--gray   { background: var(--gray-200); color: var(--gray-700); }

/* ============================================================
   PROCESS STEPS
   ============================================================ */

.steps {
  counter-reset: step-counter;
  display: flex;
  flex-direction: column;
  gap: 0;
}

.step {
  display: grid;
  grid-template-columns: 60px 1fr;
  gap: 24px;
  padding: 32px 0;
  border-bottom: 1px solid var(--gray-200);
  align-items: start;
  counter-increment: step-counter;
}

.step:last-child { border-bottom: none; }

.step__number {
  width: 52px;
  height: 52px;
  background: linear-gradient(135deg, var(--blue-600), var(--blue-500));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-size: 1.3rem;
  font-weight: 800;
  flex-shrink: 0;
  font-family: var(--font-mono);
  box-shadow: 0 4px 12px rgba(37,99,196,0.3);
}

.step__content h4 {
  margin-bottom: 8px;
  font-size: 1.1rem;
}

.step__content p {
  font-size: 0.9rem;
  color: var(--gray-600);
  margin-bottom: 0;
}

/* ============================================================
   CTA SECTION
   ============================================================ */

.cta-section {
  background: linear-gradient(135deg, var(--blue-900) 0%, var(--blue-700) 100%);
  padding: 80px 0;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.cta-section::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(circle at 30% 50%, rgba(37,99,196,0.2) 0%, transparent 50%),
    radial-gradient(circle at 70% 50%, rgba(6,182,212,0.1) 0%, transparent 40%);
}

.cta-section::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.025) 1px, transparent 1px);
  background-size: 50px 50px;
}

.cta-section__inner {
  position: relative;
  z-index: 1;
}

.cta-section h2 {
  color: var(--white);
  margin-bottom: 16px;
}

.cta-section p {
  color: var(--blue-200);
  margin-bottom: 36px;
  font-size: 1.1rem;
  max-width: 560px;
  margin-left: auto;
  margin-right: auto;
}

/* ============================================================
   FOOTER
   ============================================================ */

.footer {
  background: var(--blue-900);
  color: var(--blue-200);
  padding: 60px 0 0;
  border-top: 1px solid var(--blue-800);
}

.footer__grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer__brand .navbar__logo-name {
  font-size: 1rem;
  color: var(--white);
  display: block;
  margin-bottom: 4px;
}

.footer__brand p {
  font-size: 0.875rem;
  color: var(--blue-400);
  margin-top: 12px;
  line-height: 1.6;
}

.footer__contact {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.footer__contact-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.82rem;
  color: var(--blue-300);
}

.footer__contact-item svg {
  width: 14px;
  height: 14px;
  fill: var(--blue-500);
  flex-shrink: 0;
}

.footer__col h5 {
  color: var(--white);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 20px;
}

.footer__col ul li {
  margin-bottom: 10px;
}

.footer__col ul a {
  color: var(--blue-400);
  font-size: 0.875rem;
  transition: var(--transition);
}

.footer__col ul a:hover {
  color: var(--white);
}

.footer__bottom {
  border-top: 1px solid var(--blue-800);
  padding: 20px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.8rem;
  color: var(--blue-600);
}

.footer__bottom a {
  color: var(--blue-500);
}

.footer__bottom a:hover {
  color: var(--blue-300);
}

.footer__disclaimer {
  background: var(--blue-800);
  border-top: 1px solid var(--blue-700);
  padding: 16px 24px;
  text-align: center;
  font-size: 0.78rem;
  color: var(--blue-400);
  line-height: 1.5;
}

/* ============================================================
   SIDEBAR LAYOUT
   ============================================================ */

.content-with-sidebar {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 48px;
  align-items: start;
}

.sidebar {
  position: sticky;
  top: 90px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.sidebar__widget {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-xl);
  padding: 24px;
}

.sidebar__widget h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--gray-500);
  margin-bottom: 16px;
  font-weight: 700;
}

.sidebar__links li {
  border-bottom: 1px solid var(--gray-100);
  padding: 10px 0;
}

.sidebar__links li:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.sidebar__links a {
  font-size: 0.875rem;
  color: var(--blue-600);
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 8px;
}

.sidebar__links a::before {
  content: '→';
  color: var(--blue-400);
  font-size: 0.75rem;
}

.sidebar__links a:hover {
  color: var(--blue-400);
}

/* ============================================================
   INLINE HIGHLIGHT
   ============================================================ */

.highlight {
  background: var(--blue-50);
  border: 1px solid var(--blue-200);
  border-radius: var(--radius-lg);
  padding: 28px 32px;
  margin: 32px 0;
}

.highlight--dark {
  background: var(--blue-900);
  border-color: var(--blue-700);
  color: var(--white);
}

.highlight--dark p {
  color: var(--blue-200);
}

.highlight--dark h3,
.highlight--dark h4 {
  color: var(--white);
}

/* ============================================================
   TECH TAGS / LABELS
   ============================================================ */

.tech-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 20px 0;
}

.tech-tag {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  padding: 5px 12px;
  background: var(--blue-900);
  color: var(--blue-200);
  border: 1px solid var(--blue-700);
  border-radius: var(--radius-sm);
}

/* ============================================================
   ACCORDION
   ============================================================ */

.accordion {
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-xl);
  overflow: hidden;
}

.accordion__item {
  border-bottom: 1px solid var(--gray-200);
}

.accordion__item:last-child {
  border-bottom: none;
}

.accordion__trigger {
  width: 100%;
  padding: 20px 24px;
  background: var(--white);
  border: none;
  text-align: left;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--blue-900);
  transition: var(--transition);
  font-family: var(--font-main);
}

.accordion__trigger:hover {
  background: var(--gray-50);
  color: var(--blue-500);
}

.accordion__trigger svg {
  width: 20px;
  height: 20px;
  fill: var(--gray-400);
  transition: transform 0.3s ease;
  flex-shrink: 0;
}

.accordion__trigger.open svg {
  transform: rotate(180deg);
}

.accordion__body {
  display: none;
  padding: 0 24px 20px;
  background: var(--gray-50);
}

.accordion__body.open {
  display: block;
}

.accordion__body p {
  font-size: 0.9rem;
  color: var(--gray-600);
  margin: 16px 0 0;
}

/* ============================================================
   NOTIFICATION BANNER
   ============================================================ */

.notice-banner {
  background: linear-gradient(90deg, var(--blue-700), var(--blue-600));
  padding: 12px 24px;
  text-align: center;
  font-size: 0.82rem;
  color: var(--blue-100);
}

.notice-banner strong {
  color: var(--white);
}

/* ============================================================
   RESPONSIVE
   ============================================================ */

@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .footer__grid { grid-template-columns: 1fr 1fr; gap: 32px; }
  .content-with-sidebar { grid-template-columns: 1fr; }
  .sidebar { position: static; }
  .stats-row { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .section { padding: 56px 0; }
  .grid-2 { grid-template-columns: 1fr; gap: 32px; }
  .grid-3 { grid-template-columns: 1fr; }
  .arch-diagram { grid-template-columns: 1fr; }
  .feature-block { grid-template-columns: 1fr; gap: 32px; }
  .feature-block--reverse .feature-block__visual { order: 0; }
  .flow { gap: 12px; }
  .flow__arrow { display: none; }
  .toc__list { grid-template-columns: 1fr; }
  .hero { padding: 60px 0; }
  .page-hero { padding: 50px 0; }

  .navbar__nav { display: none; }
  .navbar__toggle { display: flex; }
  .navbar__nav.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 68px;
    left: 0;
    right: 0;
    background: var(--blue-900);
    padding: 16px;
    gap: 4px;
    border-bottom: 1px solid var(--blue-800);
  }

  .btn-group { flex-direction: column; align-items: flex-start; }
  .footer__grid { grid-template-columns: 1fr; gap: 32px; }
  .footer__bottom { flex-direction: column; gap: 8px; text-align: center; }
  .stats-row { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 480px) {
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.5rem; }
  .container { padding: 0 16px; }
  .card { padding: 24px; }
  .diagram { padding: 24px; }
  .stats-row { grid-template-columns: 1fr; }
}

/* ============================================================
   UTILITIES
   ============================================================ */

.mt-0  { margin-top: 0; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mt-48 { margin-top: 48px; }
.mb-0  { margin-bottom: 0; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mb-32 { margin-bottom: 32px; }
.mb-48 { margin-bottom: 48px; }

.fw-500 { font-weight: 500; }
.fw-600 { font-weight: 600; }
.fw-700 { font-weight: 700; }

.text-blue    { color: var(--blue-500); }
.text-gray    { color: var(--gray-500); }
.text-white   { color: var(--white); }
.text-mono    { font-family: var(--font-mono); }

.divider {
  height: 1px;
  background: var(--gray-200);
  margin: 40px 0;
}

.divider--dark {
  background: var(--blue-800);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
}