/* 
  青云梯机场 - 视觉设计系统：层门递进系统
  Fixed Palette: Light modern neutral, Cyan-Gray, Cyan-Green, Sand, Terracotta
*/

:root {
  /* Colors */
  --bg: #F8FAF9;
  --surface: #FFFFFF;
  --surface-alt: #EFF2F1;
  --text-main: #1E2729;
  --text-body: #5A6466;
  --text-muted: #879092;
  --cyan-gray: #47636B;
  --dark-cyan: #385259;
  --cyan-green: #587269;
  --dark-cyan-green: #455C54;
  --sand: #A27D5C;
  --terracotta: #AF7054;
  --bg-cyan-light: #EDF2F1;
  --bg-green-light: #EEF2EF;
  --bg-warm-light: #F6EFE8;
  --border: #DCE2DF;
  --border-accent: #AAB8B3;

  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;
  --line-height-body: 1.8;
  --max-width: 1200px;
  --max-width-article: 800px;
}

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

html {
  font-family: var(--font-family);
  font-size: 16px;
  color: var(--text-body);
  background-color: var(--bg);
  scroll-behavior: smooth;
  line-height: var(--line-height-body);
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
}

/* Focus Visible Accessibility */
a:focus-visible,
button:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--cyan-gray);
  outline-offset: 3px;
}

/* Typography elements */
h1, h2, h3, h4, h5, h6 {
  color: var(--text-main);
  font-weight: 600;
  line-height: 1.3;
}

h1 {
  font-size: clamp(2rem, 4vw + 1rem, 3.2rem);
  letter-spacing: -0.02em;
}

h2 {
  font-size: clamp(1.5rem, 2.5vw + 1rem, 2.2rem);
  margin-bottom: 1rem;
  letter-spacing: -0.01em;
}

h3 {
  font-size: clamp(1.15rem, 1.5vw + 0.8rem, 1.5rem);
  margin-bottom: 0.75rem;
}

p {
  margin-bottom: 1.25rem;
  color: var(--text-body);
}

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

a {
  color: var(--cyan-gray);
  text-decoration: none;
  transition: color 0.2s ease, border-color 0.2s ease;
}

a:hover {
  color: var(--dark-cyan);
}

/* Base Container */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Buttons & CTAs */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.75rem;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 2px;
  cursor: pointer;
  transition: all 0.2s ease;
  text-decoration: none;
  border: 1px solid transparent;
}

.btn-primary {
  background-color: var(--dark-cyan-green);
  color: #FFFFFF;
  border-color: var(--dark-cyan-green);
}

.btn-primary:hover {
  background-color: var(--cyan-green);
  color: #FFFFFF;
  border-color: var(--cyan-green);
  transform: translateY(-1px);
}

.btn-secondary {
  background-color: var(--surface);
  color: var(--text-main);
  border-color: var(--border-accent);
}

.btn-secondary:hover {
  background-color: var(--surface-alt);
  color: var(--text-main);
  border-color: var(--cyan-gray);
}

.btn-link {
  background: transparent;
  color: var(--cyan-gray);
  padding: 0.5rem 0;
  font-weight: 500;
}

.btn-link:hover {
  color: var(--dark-cyan);
  text-decoration: underline;
}

/* Tag / Badge */
.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  background-color: var(--bg-cyan-light);
  color: var(--cyan-gray);
  border: 1px solid var(--border);
  margin-bottom: 0.5rem;
}

.badge-terracotta {
  background-color: var(--bg-warm-light);
  color: var(--terracotta);
  border-color: rgba(175, 112, 84, 0.3);
}

.badge-green {
  background-color: var(--bg-green-light);
  color: var(--dark-cyan-green);
  border-color: rgba(88, 114, 105, 0.3);
}

/* Header Navbar */
.site-header {
  height: 70px;
  background-color: var(--bg);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
}

.brand-text-group {
  display: flex;
  flex-direction: column;
}

.brand-name {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: 0.02em;
  line-height: 1.2;
}

.brand-sub {
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.04em;
}

.main-nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.nav-link {
  font-size: 0.92rem;
  color: var(--text-body);
  position: relative;
  padding: 0.5rem 0;
}

.nav-link:hover,
.nav-link.active {
  color: var(--cyan-gray);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 20px;
  height: 2px;
  background-color: var(--cyan-gray);
}

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

/* Mobile Menu Toggle */
.mobile-menu-btn {
  display: none;
  background: none;
  border: 1px solid var(--border);
  padding: 0.4rem 0.75rem;
  font-size: 0.9rem;
  color: var(--text-main);
  cursor: pointer;
  border-radius: 2px;
}

/* Mobile Nav Drawer */
.mobile-nav-drawer {
  display: none;
  position: fixed;
  top: 70px;
  left: 0;
  width: 100%;
  background-color: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 1.5rem;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
  z-index: 99;
  flex-direction: column;
  gap: 1rem;
}

.mobile-nav-drawer.open {
  display: flex;
}

.mobile-nav-drawer .nav-link {
  font-size: 1rem;
  border-bottom: 1px solid var(--surface-alt);
  padding-bottom: 0.75rem;
}

/* ==================================================
   “层门递进系统” - CORE OPEN FRAME STYLES
   ================================================== */

/* Hero Section */
.hero-section {
  padding: 3.5rem 0 4rem;
  position: relative;
  background-color: var(--bg);
  min-height: 640px;
  display: flex;
  align-items: center;
}

/* Layered Frame Stack Container */
.layered-portal {
  position: relative;
  width: 100%;
  padding: 2.5rem;
  background-color: transparent;
}

/* Layer 1: Largest Frame */
.portal-layer-1 {
  position: relative;
  border: 1px solid var(--border);
  padding: 2.5rem 2rem;
  background-color: var(--surface);
}

/* Open Gap 1: Top Right Missing Segment */
.portal-layer-1::before {
  content: '';
  position: absolute;
  top: -1px;
  right: 60px;
  width: 120px;
  height: 3px;
  background-color: var(--bg);
  z-index: 2;
}

.gap-label-1 {
  position: absolute;
  top: -14px;
  right: 70px;
  background-color: var(--bg);
  padding: 0 8px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--cyan-gray);
  z-index: 3;
}

/* Layer 2: Second Frame shifted down-right */
.portal-layer-2 {
  position: relative;
  border: 1px solid var(--border-accent);
  margin-top: 1.5rem;
  padding: 2rem 1.75rem;
  background-color: var(--bg);
  transform: translate(12px, 0);
}

/* Open Gap 2: Bottom Left Missing Segment */
.portal-layer-2::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 50px;
  width: 100px;
  height: 3px;
  background-color: var(--bg);
  z-index: 2;
}

.gap-label-2 {
  position: absolute;
  bottom: -12px;
  left: 60px;
  background-color: var(--bg);
  padding: 0 8px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--sand);
  z-index: 3;
}

/* Layer 3: Third Frame shifted further */
.portal-layer-3 {
  position: relative;
  border: 1px solid var(--cyan-green);
  margin-top: 1.25rem;
  padding: 1.75rem 1.5rem;
  background-color: var(--surface);
  transform: translate(8px, 0);
}

/* Open Gap 3: Right Side Missing Segment */
.portal-layer-3::before {
  content: '';
  position: absolute;
  right: -1px;
  top: 30px;
  width: 3px;
  height: 60px;
  background-color: var(--surface);
  z-index: 2;
}

.gap-label-3 {
  position: absolute;
  top: 45px;
  right: -35px;
  transform: rotate(90deg);
  background-color: var(--surface);
  padding: 0 6px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--dark-cyan-green);
  z-index: 3;
}

/* Layer 4: Deepest Guide Bar */
.portal-layer-4 {
  position: relative;
  border-left: 3px solid var(--terracotta);
  padding-left: 1.25rem;
  margin-top: 1.5rem;
  background-color: var(--bg-warm-light);
  padding: 1rem 1.25rem;
}

.hero-meta-strip {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.hero-tag {
  color: var(--cyan-gray);
  font-weight: 600;
}

.hero-title {
  font-size: clamp(1.8rem, 3.5vw, 2.75rem);
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.25;
  margin-bottom: 1rem;
}

.hero-subhead {
  font-size: 1.15rem;
  color: var(--cyan-gray);
  font-weight: 500;
  margin-bottom: 1rem;
}

.hero-body {
  font-size: 1rem;
  color: var(--text-body);
  max-width: 820px;
  margin-bottom: 1.75rem;
}

.hero-actions {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 2rem;
}

/* Hero Anchor Links Bar (4 Layers navigation) */
.hero-anchor-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.75rem;
  margin-top: 1.5rem;
  padding-top: 1.25rem;
  border-top: 1px dashed var(--border-accent);
}

.hero-anchor-card {
  display: flex;
  flex-direction: column;
  padding: 0.75rem 1rem;
  background-color: var(--surface-alt);
  border: 1px solid var(--border);
  transition: all 0.2s ease;
  position: relative;
}

.hero-anchor-card:hover {
  border-color: var(--cyan-gray);
  background-color: var(--surface);
  transform: translateY(-2px);
}

.hero-anchor-num {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--terracotta);
}

.hero-anchor-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-main);
}

.hero-anchor-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* ==================================================
   SECTION COMMON STYLES
   ================================================== */

.section {
  padding: 4.5rem 0;
  border-bottom: 1px solid var(--border);
  position: relative;
}

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

.section-header {
  margin-bottom: 2.5rem;
  position: relative;
}

.section-num {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--sand);
  letter-spacing: 0.1em;
  margin-bottom: 0.25rem;
  display: block;
}

.section-title {
  font-size: clamp(1.5rem, 2.5vw, 2.2rem);
  color: var(--text-main);
  margin-bottom: 0.75rem;
}

.section-lead {
  font-size: 1.05rem;
  color: var(--text-body);
  max-width: 800px;
}

/* Open Frame Section Wrapper */
.open-section-frame {
  position: relative;
  border: 1px solid var(--border);
  padding: 2rem;
  background-color: var(--surface);
}

.open-section-frame::before {
  content: '';
  position: absolute;
  top: -1px;
  left: 40px;
  width: 80px;
  height: 3px;
  background-color: var(--bg);
}

.section-frame-gap-tag {
  position: absolute;
  top: -12px;
  left: 45px;
  background-color: var(--bg);
  padding: 0 6px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--cyan-gray);
}

/* ==================================================
   SECTION 01 & 07: PRICING (层门价目 System)
   ================================================== */

.pricing-portal-wrapper {
  position: relative;
  padding: 1.5rem;
  background-color: var(--surface-alt);
  border: 1px solid var(--border);
}

/* Outer frame of Pricing */
.pricing-outer-frame {
  border: 1px solid var(--border-accent);
  padding: 1.5rem;
  background-color: var(--bg);
  position: relative;
}

.pricing-outer-frame::before {
  content: '';
  position: absolute;
  top: -1px;
  right: 50px;
  width: 70px;
  height: 3px;
  background-color: var(--surface-alt);
}

.pricing-grid-layout {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: 1.25rem;
  align-items: stretch;
}

/* Outer Layer Items (Tier 1 & 5) */
.plan-item-outer {
  grid-column: span 3;
  background-color: var(--surface);
  border: 1px solid var(--border);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

/* Middle Layer Items (Tier 2 & 4) */
.plan-item-mid {
  grid-column: span 3;
  background-color: var(--surface);
  border: 1px solid var(--border-accent);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  position: relative;
}

.plan-item-mid::before {
  content: '';
  position: absolute;
  top: 0;
  left: 20px;
  right: 20px;
  height: 2px;
  background-color: var(--cyan-gray);
}

/* Innermost Core Layer Item (Tier 3 - Main Plan) */
.plan-item-core {
  grid-column: span 6;
  background-color: var(--bg-green-light);
  border: 2px solid var(--cyan-green);
  padding: 2rem 1.75rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  position: relative;
  box-shadow: 0 8px 24px rgba(30, 39, 41, 0.03);
}

.plan-item-core::before {
  content: '';
  position: absolute;
  top: -2px;
  right: 40px;
  width: 90px;
  height: 4px;
  background-color: var(--bg);
}

.plan-core-tag {
  position: absolute;
  top: -14px;
  right: 45px;
  background-color: var(--terracotta);
  color: #FFFFFF;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.75rem;
  border-radius: 2px;
}

.plan-num {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--cyan-gray);
  margin-bottom: 0.25rem;
}

.plan-name {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
}

.plan-price-group {
  margin: 1rem 0;
}

.plan-price {
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1;
}

.plan-price-unit {
  font-size: 0.9rem;
  color: var(--text-muted);
  font-weight: normal;
}

.plan-traffic {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--dark-cyan);
  margin-bottom: 0.5rem;
}

.plan-desc {
  font-size: 0.88rem;
  color: var(--text-body);
  margin-bottom: 1.25rem;
}

.pricing-disclaimer {
  margin-top: 1.5rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  padding-top: 1rem;
}

/* ==================================================
   SECTION 02: NODE REGIONS (节点地区)
   ================================================== */

.node-portal-container {
  position: relative;
  border: 1px solid var(--border);
  padding: 2rem;
  background-color: var(--surface);
}

.node-outer-label {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--cyan-gray);
  background-color: var(--bg-cyan-light);
  padding: 0.25rem 0.75rem;
  margin-bottom: 1.5rem;
  border: 1px solid var(--border);
}

.node-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.node-layer-box {
  border: 1px solid var(--border);
  padding: 1.5rem;
  background-color: var(--bg);
  position: relative;
}

.node-layer-box-inner {
  border-left: 2px solid var(--cyan-green);
  padding-left: 1rem;
}

.node-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.node-conclusion {
  font-size: 0.92rem;
  color: var(--cyan-gray);
  font-weight: 600;
  margin-bottom: 0.75rem;
}

.node-detail-list {
  list-style: none;
  font-size: 0.88rem;
  color: var(--text-body);
}

.node-detail-list li {
  margin-bottom: 0.4rem;
  padding-left: 1rem;
  position: relative;
}

.node-detail-list li::before {
  content: '▪';
  position: absolute;
  left: 0;
  color: var(--cyan-green);
}

.node-link-more {
  margin-top: 1rem;
  display: inline-block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--cyan-gray);
}

/* ==================================================
   SECTION 03: LINE KNOWLEDGE & HTML TABLE (线路知识)
   ================================================== */

.line-portal-box {
  position: relative;
  border: 1px solid var(--border);
  padding: 2rem;
  background-color: var(--surface);
}

.line-intro-block {
  margin-bottom: 1.5rem;
  padding: 1.25rem;
  background-color: var(--surface-alt);
  border-left: 3px solid var(--cyan-gray);
}

.line-table-wrapper {
  width: 100%;
  overflow-x: auto;
  margin-top: 1.5rem;
}

.line-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.92rem;
}

.line-table th {
  background-color: var(--surface-alt);
  color: var(--text-main);
  font-weight: 600;
  padding: 0.9rem 1rem;
  border-bottom: 2px solid var(--border-accent);
}

.line-table td {
  padding: 0.9rem 1rem;
  border-bottom: 1px solid var(--border);
  color: var(--text-body);
}

.line-table tr:hover {
  background-color: var(--bg);
}

.line-tag {
  font-weight: 600;
  color: var(--dark-cyan);
}

/* ==================================================
   SECTION 04 & 05: AI & STREAMING (AI与流媒体)
   ================================================== */

.services-portal-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2rem;
}

.service-portal-card {
  border: 1px solid var(--border);
  padding: 2rem;
  background-color: var(--surface);
  position: relative;
}

.service-portal-card::before {
  content: '';
  position: absolute;
  top: -1px;
  left: 30px;
  width: 60px;
  height: 3px;
  background-color: var(--bg);
}

.service-main-group {
  margin-bottom: 1.5rem;
}

.service-item-row {
  border-bottom: 1px solid var(--border);
  padding: 0.85rem 0;
}

.service-item-row:last-child {
  border-bottom: none;
}

.service-item-name {
  font-weight: 600;
  color: var(--text-main);
  font-size: 1rem;
}

.service-item-desc {
  font-size: 0.88rem;
  color: var(--text-body);
  margin-top: 0.2rem;
}

.service-sub-group {
  background-color: var(--bg);
  padding: 1rem;
  border: 1px solid var(--border);
  margin-top: 1rem;
}

.service-sub-title {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--cyan-gray);
  margin-bottom: 0.5rem;
}

/* ==================================================
   SECTION 06: CLIENTS (客户端)
   ================================================== */

.client-portal-stack {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.client-device-layer {
  border: 1px solid var(--border);
  padding: 1.75rem;
  background-color: var(--surface);
  position: relative;
}

.client-device-layer-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-main);
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.75rem;
  margin-bottom: 1rem;
}

.client-item-box {
  margin-bottom: 1.25rem;
}

.client-item-box:last-child {
  margin-bottom: 0;
}

.client-item-name {
  font-weight: 600;
  font-size: 1rem;
  color: var(--cyan-gray);
}

.client-item-steps {
  font-size: 0.88rem;
  color: var(--text-body);
  margin-top: 0.3rem;
  line-height: 1.6;
}

/* ==================================================
   SECTION 08: REVIEW SUMMARY (深度评测)
   ================================================== */

.review-portal-box {
  border: 1px solid var(--border-accent);
  padding: 2.25rem;
  background-color: var(--surface);
  position: relative;
}

.review-portal-box::before {
  content: '';
  position: absolute;
  top: -1px;
  right: 80px;
  width: 100px;
  height: 3px;
  background-color: var(--bg);
}

.review-summary-grid {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: 2rem;
  align-items: center;
}

.review-summary-content h3 {
  font-size: 1.35rem;
  color: var(--text-main);
  margin-bottom: 0.75rem;
}

.review-checklist {
  list-style: none;
  margin: 1rem 0 1.5rem;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.5rem;
  font-size: 0.9rem;
}

.review-checklist li {
  padding-left: 1.2rem;
  position: relative;
}

.review-checklist li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: var(--cyan-green);
  font-weight: bold;
}

/* ==================================================
   SECTION 09: ARTICLES & GUIDES (阅读层门 System)
   ================================================== */

.guides-portal-container {
  position: relative;
}

.reading-layers-stack {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.reading-layer-group {
  border: 1px solid var(--border);
  padding: 1.5rem;
  background-color: var(--surface);
  position: relative;
}

.reading-layer-header {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--terracotta);
  margin-bottom: 1rem;
  letter-spacing: 0.05em;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.reading-articles-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.article-card-item {
  border: 1px solid var(--border);
  padding: 1.25rem;
  background-color: var(--bg);
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.article-card-item:hover {
  border-color: var(--cyan-gray);
  background-color: var(--surface);
  transform: translateY(-2px);
}

.article-card-cat {
  font-size: 0.75rem;
  color: var(--cyan-gray);
  font-weight: 600;
  margin-bottom: 0.3rem;
}

.article-card-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 0.5rem;
  line-height: 1.4;
}

.article-card-excerpt {
  font-size: 0.85rem;
  color: var(--text-body);
  margin-bottom: 1rem;

  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.article-card-meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border);
  padding-top: 0.5rem;
  margin-top: auto;
}

/* ==================================================
   SECTION 10: TROUBLESHOOTING (网络排障 由外到内)
   ================================================== */

.trouble-portal-stack {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  position: relative;
}

.trouble-step-layer {
  border: 1px solid var(--border);
  padding: 1.25rem 1.5rem;
  background-color: var(--surface);
  display: flex;
  align-items: flex-start;
  gap: 1.5rem;
  position: relative;
}

.trouble-step-num {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--cyan-gray);
  background-color: var(--bg-cyan-light);
  padding: 0.3rem 0.6rem;
  border: 1px solid var(--border);
  white-space: nowrap;
}

.trouble-step-content h3 {
  font-size: 1.1rem;
  margin-bottom: 0.3rem;
}

.trouble-step-content p {
  font-size: 0.9rem;
  color: var(--text-body);
}

/* ==================================================
   SECTION 11: FAQ (问答层门 System)
   ================================================== */

.faq-portal-wrapper {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.faq-layer-group {
  border: 1px solid var(--border);
  padding: 1.5rem;
  background-color: var(--surface);
}

.faq-layer-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--cyan-gray);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

.faq-accordion-list {
  display: flex;
  flex-direction: column;
}

.faq-item {
  border-bottom: 1px solid var(--border);
}

.faq-item:last-child {
  border-bottom: none;
}

.faq-question-btn {
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  padding: 1rem 0;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-main);
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  font-family: inherit;
}

.faq-question-btn:hover {
  color: var(--cyan-gray);
}

.faq-icon {
  font-size: 1.2rem;
  transition: transform 0.2s ease;
  color: var(--cyan-gray);
}

.faq-item.open .faq-icon {
  transform: rotate(45deg);
}

.faq-answer-panel {
  display: none;
  padding-bottom: 1.25rem;
  font-size: 0.92rem;
  color: var(--text-body);
  line-height: 1.8;
}

.faq-item.open .faq-answer-panel {
  display: block;
}

/* ==================================================
   FOOTER (浅青灰 紧凑 Style)
   ================================================== */

.site-footer {
  background-color: var(--surface-alt);
  color: var(--text-body);
  border-top: 1px solid var(--border);
  padding: 3rem 0 1.5rem;
  margin-top: auto;
  font-size: 0.88rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2.2fr 1fr 1fr 1fr 1fr;
  gap: 2rem;
  margin-bottom: 2.5rem;
}

.footer-brand-col {
  border-left: 2px solid var(--cyan-gray);
  padding-left: 1rem;
}

.footer-brand-name {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.4rem;
}

.footer-brand-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.footer-col-title {
  font-size: 0.92rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.85rem;
}

.footer-link-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.footer-link-list a {
  color: var(--text-body);
  font-size: 0.85rem;
}

.footer-link-list a:hover {
  color: var(--cyan-gray);
}

.footer-bottom-bar {
  border-top: 1px solid var(--border);
  padding-top: 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.82rem;
  color: var(--text-muted);
}

.friendly-links {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.friendly-links a {
  color: var(--text-body);
}

.friendly-links a:hover {
  color: var(--cyan-gray);
}

/* ==================================================
   ARTICLE & CATEGORY INNER PAGES LAYOUT
   ================================================== */

.page-header {
  padding: 2.5rem 0 2rem;
  background-color: var(--bg);
  border-bottom: 1px solid var(--border);
}

.breadcrumb-nav {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.breadcrumb-nav a {
  color: var(--text-muted);
}

.breadcrumb-nav a:hover {
  color: var(--cyan-gray);
}

.article-hero-frame {
  position: relative;
  border: 1px solid var(--border);
  padding: 2rem;
  background-color: var(--surface);
}

.article-hero-frame::before {
  content: '';
  position: absolute;
  top: -1px;
  right: 40px;
  width: 80px;
  height: 3px;
  background-color: var(--bg);
}

.article-meta-badge {
  position: absolute;
  bottom: -12px;
  right: 45px;
  background-color: var(--bg-cyan-light);
  border: 1px solid var(--border);
  padding: 0.2rem 0.6rem;
  font-size: 0.75rem;
  color: var(--cyan-gray);
}

.article-layout-grid {
  display: grid;
  grid-template-columns: 1fr 240px;
  gap: 2.5rem;
  padding: 3rem 0;
}

.article-content-main {
  max-width: var(--max-width-article);

}

.quick-conclusion-box {
  border: 1px solid var(--cyan-green);
  background-color: var(--bg-green-light);
  padding: 1.25rem 1.5rem;
  margin-bottom: 2rem;
  position: relative;
}

.quick-conclusion-box h3 {
  font-size: 1rem;
  color: var(--dark-cyan-green);
  margin-bottom: 0.4rem;
}

.quick-conclusion-box p {
  font-size: 0.95rem;
  color: var(--text-main);
}

/* Article H2 open line style */
.article-content-main h2 {
  position: relative;
  padding-left: 0.85rem;
  border-left: 3px solid var(--cyan-gray);
  margin: 2.5rem 0 1rem;
  font-size: 1.5rem;
}

.article-content-main h3 {
  margin: 1.75rem 0 0.75rem;
  font-size: 1.2rem;
}

.article-content-main ul, 
.article-content-main ol {
  margin-bottom: 1.25rem;
  padding-left: 1.5rem;
}

.article-content-main li {
  margin-bottom: 0.4rem;
}

/* Article Sidebar TOC */
.article-toc-sidebar {
  position: sticky;
  top: 90px;
  height: fit-content;
  border: 1px solid var(--border);
  padding: 1.25rem;
  background-color: var(--surface);
  font-size: 0.85rem;
}

.toc-title {
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.75rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border);
}

.toc-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.toc-list a {
  color: var(--text-body);
  display: block;
}

.toc-list a:hover {
  color: var(--cyan-gray);
}

.related-articles-section {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

/* ==================================================
   RESPONSIVE MEDIA QUERIES
   ================================================== */

@media (max-width: 1024px) {
  .pricing-grid-layout {
    grid-template-columns: repeat(6, 1fr);
  }
  .plan-item-outer, .plan-item-mid {
    grid-column: span 3;
  }
  .plan-item-core {
    grid-column: span 6;
  }
  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr;
  }
}

@media (max-width: 768px) {
  /* Header Mobile */
  .main-nav, .nav-cta {
    display: none;
  }
  .mobile-menu-btn {
    display: block;
  }

  /* Hero Mobile */
  .hero-section {
    padding: 2rem 0 3rem;
    min-height: auto;
  }
  .layered-portal {
    padding: 0;
  }
  .portal-layer-1, .portal-layer-2, .portal-layer-3 {
    transform: none;
    padding: 1.25rem 1rem;
    margin-top: 1rem;
  }
  .gap-label-1, .gap-label-2, .gap-label-3 {
    font-size: 0.75rem;
  }
  .hero-anchor-bar {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Pricing Mobile */
  .pricing-grid-layout {
    grid-template-columns: 1fr;
  }
  .plan-item-outer, .plan-item-mid, .plan-item-core {
    grid-column: span 1;
  }

  /* Grids to 1 col */
  .node-grid,
  .services-portal-grid,
  .client-portal-stack,
  .review-summary-grid,
  .reading-articles-grid {
    grid-template-columns: 1fr;
  }

  .review-checklist {
    grid-template-columns: 1fr;
  }

  .article-layout-grid {
    grid-template-columns: 1fr;
  }
  .article-toc-sidebar {
    display: none; /* Collapsible or hidden on mobile TOC */
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
}

/* Accessibility: Prefers Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}