/* ========================================
       CSS Custom Properties (Design Tokens)
       ======================================== */
    :root {
      --color-aws-dark: #232F3E;
      --color-aws-orange: #dc7600;
      --color-aws-orange-original: #FF9900;
      --color-aws-orange-hover: #EC7211;
      --color-text-primary: #374151;
      --color-text-secondary: #6B7280;
      --color-text-white: #FFFFFF;
      --color-bg-light: #F9FAFB;
      --color-bg-white: #FFFFFF;
      --color-border-light: #E5E7EB;
      --color-success: #10B981;
      --color-warning: #F59E0B;
      --color-error: #EF4444;
      --color-info: #3B82F6;
      --spacing-xs: 5px;
      --spacing-sm: 10px;
      --spacing-md: 15px;
      --spacing-base: 20px;
      --spacing-lg: 25px;
      --spacing-xl: 30px;
      --spacing-2xl: 40px;
      --spacing-3xl: 60px;
      --radius-sm: 6px;
      --radius-md: 8px;
      --radius-base: 10px;
      --radius-lg: 15px;
      --radius-xl: 20px;
      --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
      --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
      --shadow-lg: 0 10px 40px rgba(0,0,0,0.15);
      --transition-base: 0.3s ease;
      --font-weight-medium: 500;
      --font-weight-semibold: 600;
      --font-weight-bold: 700;
    }

    /* ========================================
       Reset & Base
       ======================================== */
    * { margin: 0; padding: 0; box-sizing: border-box; }
    html { scroll-behavior: smooth; }

    body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background: linear-gradient(135deg, #667eea 0%, #764ba2 25%, #9333EA 50%, #0369A1 75%, #00f2fe 100%);
      padding: 20px;
      padding-top: 80px;
      line-height: 1.7;
      font-size: 20px;
      color: var(--color-text-primary);
    }

    /* ========================================
       Fixed Navigation Header
       ======================================== */
    .fixed-nav-header {
      position: fixed;
      top: 0; left: 0; right: 0;
      height: 60px;
      background: linear-gradient(135deg, var(--color-aws-dark) 0%, #374151 100%);
      box-shadow: 0 2px 10px rgba(0,0,0,0.3);
      z-index: 1002;
      display: flex;
      align-items: center;
    }
    .fixed-nav-container {
      width: 100%;
      max-width: 1200px;
      margin: 0 auto;
      padding: 0 var(--spacing-xl);
      display: flex;
      align-items: center;
      justify-content: space-between;
    }
    .fixed-nav-logo {
      font-size: 1.3em;
      font-weight: var(--font-weight-bold);
      color: var(--color-aws-orange-original);
      text-decoration: none;
    }
    .fixed-nav-links { display: flex; gap: 20px; }
    .fixed-nav-links a {
      color: var(--color-text-white);
      text-decoration: none;
      font-weight: var(--font-weight-medium);
      font-size: 0.85em;
      padding: 8px 14px;
      border-radius: var(--radius-sm);
      transition: all var(--transition-base);
      white-space: nowrap;
    }
    .fixed-nav-links a:hover {
      background-color: rgba(255,153,0,0.2);
      color: var(--color-aws-orange-original);
    }

    /* ========================================
       Reading Progress Bar
       ======================================== */
    .reading-progress {
      position: fixed; top: 60px; left: 0;
      width: 100%; height: 4px;
      background-color: #E5E7EB;
      z-index: 1001;
      opacity: 0;
      transition: opacity var(--transition-base);
    }
    .reading-progress.show { opacity: 1; }
    .reading-progress-bar {
      height: 100%;
      background: linear-gradient(90deg, var(--color-aws-orange-original) 0%, var(--color-aws-orange-hover) 100%);
      width: 0%;
      transition: width 0.1s ease;
    }

    /* ========================================
       Main Container
       ======================================== */
    .container {
      max-width: 1200px;
      margin: 0 auto;
    }

    /* ========================================
       Breadcrumb
       ======================================== */
    .breadcrumb-nav {
      background-color: rgba(255,255,255,0.95);
      padding: 15px 25px;
      border-radius: var(--radius-base);
      margin-bottom: var(--spacing-xl);
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: var(--spacing-sm);
      box-shadow: var(--shadow-sm);
      font-size: 0.85em;
    }
    .breadcrumb-home {
      color: var(--color-aws-orange);
      text-decoration: none;
      font-weight: var(--font-weight-semibold);
    }
    .breadcrumb-separator { color: #9CA3AF; user-select: none; }
    .breadcrumb-current { color: var(--color-aws-orange); font-weight: var(--font-weight-bold); }

    /* ========================================
       Section Base
       ======================================== */
    .section {
      background-color: var(--color-bg-white);
      border-radius: var(--radius-xl);
      padding: var(--spacing-2xl);
      margin-bottom: var(--spacing-xl);
      box-shadow: var(--shadow-md);
    }
    .section-title {
      font-size: 1.6em;
      font-weight: var(--font-weight-bold);
      color: var(--color-text-primary);
      margin-bottom: var(--spacing-lg);
      padding-bottom: var(--spacing-sm);
      border-bottom: 3px solid var(--color-aws-orange-original);
      display: flex;
      align-items: center;
      gap: var(--spacing-sm);
    }
    .section-title .icon { font-size: 1.2em; }

    /* ========================================
       Hero Section
       ======================================== */
    .hero {
      background: linear-gradient(135deg, var(--color-aws-dark) 0%, #1a2332 100%);
      color: var(--color-text-white);
      border-radius: var(--radius-xl);
      padding: var(--spacing-3xl) var(--spacing-2xl);
      margin-bottom: var(--spacing-xl);
      box-shadow: var(--shadow-lg);
      text-align: center;
      position: relative;
      overflow: hidden;
    }
    .hero::before {
      content: '';
      position: absolute;
      top: -50%; left: -50%;
      width: 200%; height: 200%;
      background: radial-gradient(ellipse at 30% 20%, rgba(255,153,0,0.08) 0%, transparent 50%),
                  radial-gradient(ellipse at 70% 80%, rgba(59,130,246,0.06) 0%, transparent 50%);
      pointer-events: none;
    }
    .hero-badge {
      display: inline-block;
      background: rgba(255,153,0,0.2);
      color: var(--color-aws-orange-original);
      padding: 6px 20px;
      border-radius: 20px;
      font-size: 0.8em;
      font-weight: var(--font-weight-semibold);
      margin-bottom: var(--spacing-base);
      letter-spacing: 0.5px;
      position: relative;
    }
    .hero h1 {
      font-size: 2.2em;
      font-weight: var(--font-weight-bold);
      margin-bottom: var(--spacing-md);
      position: relative;
    }
    .hero-sub {
      font-size: 1.05em;
      color: rgba(255,255,255,0.8);
      margin-bottom: var(--spacing-2xl);
      position: relative;
    }

    /* Key Takeaways in Hero */
    .takeaway-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: var(--spacing-base);
      position: relative;
    }
    .takeaway-card {
      background: rgba(255,255,255,0.08);
      backdrop-filter: blur(10px);
      border: 1px solid rgba(255,255,255,0.12);
      border-radius: var(--radius-lg);
      padding: var(--spacing-lg);
      text-align: left;
      transition: all var(--transition-base);
    }
    .takeaway-card:hover {
      background: rgba(255,255,255,0.14);
      transform: translateY(-3px);
    }
    .takeaway-num {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 36px; height: 36px;
      background: var(--color-aws-orange-original);
      color: var(--color-text-white);
      border-radius: 50%;
      font-weight: var(--font-weight-bold);
      font-size: 0.9em;
      margin-bottom: var(--spacing-sm);
    }
    .takeaway-title {
      font-size: 1em;
      font-weight: var(--font-weight-bold);
      margin-bottom: 6px;
    }
    .takeaway-desc {
      font-size: 0.85em;
      color: rgba(255,255,255,0.75);
      line-height: 1.5;
    }

    /* ========================================
       Analogy Section
       ======================================== */
    .analogy-hero {
      background: linear-gradient(135deg, #FFF7ED 0%, #FFFBEB 100%);
      border: 2px solid #FDBA74;
      border-radius: var(--radius-xl);
      padding: var(--spacing-2xl);
      margin-bottom: var(--spacing-xl);
      text-align: center;
    }
    .analogy-hero .emoji-big {
      font-size: 3em;
      margin-bottom: var(--spacing-sm);
    }
    .analogy-hero h2 {
      font-size: 1.5em;
      color: var(--color-text-primary);
      margin-bottom: var(--spacing-sm);
    }
    .analogy-hero p {
      font-size: 1em;
      color: var(--color-text-secondary);
      max-width: 700px;
      margin: 0 auto;
    }

    /* Analogy Mapping Table */
    .mapping-table {
      width: 100%;
      border-collapse: separate;
      border-spacing: 0;
      margin-top: var(--spacing-lg);
      font-size: 0.95em;
    }
    .mapping-table thead th {
      background: var(--color-aws-dark);
      color: var(--color-text-white);
      padding: 14px 20px;
      text-align: left;
      font-weight: var(--font-weight-semibold);
    }
    .mapping-table thead th:first-child { border-radius: var(--radius-base) 0 0 0; }
    .mapping-table thead th:last-child { border-radius: 0 var(--radius-base) 0 0; }
    .mapping-table tbody td {
      padding: 14px 20px;
      border-bottom: 1px solid var(--color-border-light);
    }
    .mapping-table tbody tr:nth-child(even) { background-color: #FAFAFA; }
    .mapping-table tbody tr:hover { background-color: #FFF7ED; }
    .mapping-table tbody tr:last-child td:first-child { border-radius: 0 0 0 var(--radius-base); }
    .mapping-table tbody tr:last-child td:last-child { border-radius: 0 0 var(--radius-base) 0; }

    /* ========================================
       Setting Cards (2-column equal grid)
       ======================================== */
    .settings-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: var(--spacing-lg);
    }
    .setting-card {
      background: var(--color-bg-white);
      border: 2px solid var(--color-border-light);
      border-radius: var(--radius-lg);
      padding: var(--spacing-lg);
      transition: all var(--transition-base);
    }
    .setting-card:hover {
      border-color: var(--color-aws-orange-original);
      box-shadow: var(--shadow-md);
    }
    .setting-card-header {
      display: flex;
      align-items: center;
      gap: var(--spacing-sm);
      margin-bottom: var(--spacing-md);
    }
    .setting-icon {
      width: 48px; height: 48px;
      border-radius: var(--radius-base);
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 1.4em;
      flex-shrink: 0;
    }
    .setting-icon-dns { background: #EEF2FF; }
    .setting-icon-hostname { background: #ECFDF5; }
    .setting-name {
      font-size: 1em;
      font-weight: var(--font-weight-bold);
      color: var(--color-text-primary);
    }
    .setting-code {
      font-family: 'Cascadia Code', 'Fira Code', monospace;
      font-size: 0.78em;
      color: var(--color-aws-orange);
      background: #FFF7ED;
      padding: 2px 8px;
      border-radius: 4px;
    }
    .setting-desc {
      font-size: 0.9em;
      color: var(--color-text-secondary);
      margin-bottom: var(--spacing-md);
      line-height: 1.6;
    }
    .setting-details {
      font-size: 0.85em;
      background: var(--color-bg-light);
      border-radius: var(--radius-md);
      padding: var(--spacing-md);
    }
    .detail-item {
      display: flex;
      align-items: flex-start;
      gap: var(--spacing-sm);
      margin-bottom: var(--spacing-sm);
    }
    .detail-item:last-child { margin-bottom: 0; }
    .detail-dot {
      width: 8px; height: 8px;
      border-radius: 50%;
      margin-top: 8px;
      flex-shrink: 0;
    }
    .dot-blue { background: var(--color-info); }
    .dot-green { background: var(--color-success); }
    .dot-orange { background: var(--color-warning); }

    /* ========================================
       Combination Matrix (4-cell grid)
       ======================================== */
    .matrix-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: var(--spacing-base);
    }
    .matrix-cell {
      border: 2px solid var(--color-border-light);
      border-radius: var(--radius-lg);
      padding: var(--spacing-lg);
      position: relative;
      transition: all var(--transition-base);
    }
    .matrix-cell:hover {
      box-shadow: var(--shadow-md);
      transform: translateY(-2px);
    }
    .matrix-cell-header {
      display: flex;
      align-items: center;
      justify-content: space-between;
      margin-bottom: var(--spacing-md);
    }
    .matrix-label {
      font-size: 0.85em;
      font-weight: var(--font-weight-bold);
      padding: 4px 12px;
      border-radius: 20px;
    }
    .label-recommended { background: #ECFDF5; color: #059669; }
    .label-limited { background: #FFF7ED; color: #D97706; }
    .label-minimum { background: #EFF6FF; color: #2563EB; }
    .label-danger { background: #FEF2F2; color: #DC2626; }

    .matrix-settings {
      font-size: 0.8em;
      font-family: 'Cascadia Code', 'Fira Code', monospace;
      display: flex;
      gap: 8px;
      margin-bottom: var(--spacing-sm);
    }
    .setting-on {
      background: #D1FAE5;
      color: #065F46;
      padding: 3px 10px;
      border-radius: 4px;
    }
    .setting-off {
      background: #FEE2E2;
      color: #991B1B;
      padding: 3px 10px;
      border-radius: 4px;
    }
    .matrix-analogy {
      font-size: 0.88em;
      color: var(--color-text-primary);
      margin-bottom: var(--spacing-sm);
      padding: var(--spacing-sm);
      background: #FFFBEB;
      border-radius: var(--radius-sm);
      border-left: 3px solid var(--color-aws-orange-original);
    }
    .matrix-behavior {
      font-size: 0.85em;
      color: var(--color-text-secondary);
      line-height: 1.6;
    }

    /* ========================================
       SVG Diagram Container
       ======================================== */
    .svg-container {
      width: 100%;
      overflow-x: auto;
      margin: var(--spacing-lg) 0;
    }
    .svg-container svg {
      display: block;
      margin: 0 auto;
      max-width: 100%;
      height: auto;
    }

    /* ========================================
       Private Hosted Zone Requirement
       ======================================== */
    .requirement-box {
      background: linear-gradient(135deg, #EEF2FF 0%, #F0F9FF 100%);
      border: 2px solid #818CF8;
      border-radius: var(--radius-xl);
      padding: var(--spacing-2xl);
    }
    .requirement-title {
      font-size: 1.2em;
      font-weight: var(--font-weight-bold);
      color: #4338CA;
      margin-bottom: var(--spacing-md);
      display: flex;
      align-items: center;
      gap: var(--spacing-sm);
    }
    .req-conditions {
      display: grid;
      grid-template-columns: 1fr auto 1fr auto 1fr;
      gap: var(--spacing-sm);
      align-items: center;
      margin: var(--spacing-lg) 0;
    }
    .req-pill {
      background: var(--color-bg-white);
      border: 2px solid #818CF8;
      border-radius: var(--radius-base);
      padding: var(--spacing-md) var(--spacing-base);
      text-align: center;
      font-weight: var(--font-weight-semibold);
      font-size: 0.9em;
    }
    .req-pill code {
      display: block;
      font-family: 'Cascadia Code', 'Fira Code', monospace;
      font-size: 0.85em;
      color: var(--color-success);
      margin-top: 4px;
    }
    .req-operator {
      font-size: 1.8em;
      font-weight: var(--font-weight-bold);
      color: #818CF8;
      text-align: center;
    }
    .req-result {
      background: #ECFDF5;
      border: 2px solid #34D399;
      border-radius: var(--radius-base);
      padding: var(--spacing-md) var(--spacing-base);
      text-align: center;
      font-weight: var(--font-weight-semibold);
      font-size: 0.9em;
      color: #065F46;
    }

    /* ========================================
       Code Block (tabbed)
       ======================================== */
    .code-section { margin-top: var(--spacing-lg); }
    .code-tabs {
      display: flex;
      gap: 2px;
      margin-bottom: 0;
    }
    .code-tab {
      padding: 10px 20px;
      background: #E5E7EB;
      border: none;
      border-radius: var(--radius-md) var(--radius-md) 0 0;
      cursor: pointer;
      font-size: 0.8em;
      font-weight: var(--font-weight-semibold);
      color: var(--color-text-secondary);
      transition: all var(--transition-base);
      font-family: inherit;
    }
    .code-tab.active {
      background: var(--color-aws-dark);
      color: var(--color-text-white);
    }
    .code-tab:hover:not(.active) {
      background: #D1D5DB;
    }
    .code-content {
      display: none;
      background: var(--color-aws-dark);
      border-radius: 0 var(--radius-md) var(--radius-md) var(--radius-md);
      padding: var(--spacing-lg);
      overflow-x: auto;
    }
    .code-content.active { display: block; }
    .code-content pre {
      color: #E5E7EB;
      font-family: 'Cascadia Code', 'Fira Code', 'Courier New', monospace;
      font-size: 0.78em;
      line-height: 1.6;
      white-space: pre;
    }
    .code-comment { color: #6B7280; }
    .code-key { color: #93C5FD; }
    .code-value { color: #86EFAC; }
    .code-string { color: #FCD34D; }

    /* ========================================
       Best Practices / Anti-Patterns
       ======================================== */
    .practices-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: var(--spacing-lg);
    }
    .practice-card {
      border-radius: var(--radius-lg);
      padding: var(--spacing-lg);
      border: 2px solid;
    }
    .practice-do {
      background: #F0FDF4;
      border-color: #86EFAC;
    }
    .practice-dont {
      background: #FEF2F2;
      border-color: #FCA5A5;
    }
    .practice-header {
      font-size: 1.05em;
      font-weight: var(--font-weight-bold);
      margin-bottom: var(--spacing-md);
      display: flex;
      align-items: center;
      gap: var(--spacing-sm);
    }
    .practice-do .practice-header { color: #059669; }
    .practice-dont .practice-header { color: #DC2626; }
    .practice-item {
      display: flex;
      align-items: flex-start;
      gap: var(--spacing-sm);
      margin-bottom: var(--spacing-sm);
      font-size: 0.9em;
      line-height: 1.5;
    }
    .practice-item:last-child { margin-bottom: 0; }

    /* ========================================
       Use Cases
       ======================================== */
    .usecase-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: var(--spacing-lg);
    }
    .usecase-card {
      background: var(--color-bg-white);
      border: 2px solid var(--color-border-light);
      border-radius: var(--radius-lg);
      padding: var(--spacing-lg);
      transition: all var(--transition-base);
    }
    .usecase-card:hover {
      border-color: var(--color-aws-orange-original);
      box-shadow: var(--shadow-md);
    }
    .usecase-icon {
      font-size: 1.6em;
      margin-bottom: var(--spacing-sm);
    }
    .usecase-title {
      font-size: 1em;
      font-weight: var(--font-weight-bold);
      color: var(--color-text-primary);
      margin-bottom: var(--spacing-sm);
    }
    .usecase-desc {
      font-size: 0.85em;
      color: var(--color-text-secondary);
      line-height: 1.5;
      margin-bottom: var(--spacing-sm);
    }
    .usecase-settings {
      font-size: 0.78em;
      font-family: 'Cascadia Code', 'Fira Code', monospace;
      display: flex;
      gap: 6px;
      flex-wrap: wrap;
    }

    /* ========================================
       FAQ Accordion
       ======================================== */
    .faq-item {
      border: 1px solid var(--color-border-light);
      border-radius: var(--radius-base);
      margin-bottom: var(--spacing-sm);
      overflow: hidden;
      transition: all var(--transition-base);
    }
    .faq-item:hover {
      border-color: var(--color-aws-orange-original);
    }
    .faq-question {
      width: 100%;
      background: var(--color-bg-light);
      border: none;
      padding: var(--spacing-base) var(--spacing-lg);
      font-size: 0.95em;
      font-weight: var(--font-weight-semibold);
      color: var(--color-text-primary);
      cursor: pointer;
      display: flex;
      justify-content: space-between;
      align-items: center;
      text-align: left;
      font-family: inherit;
      transition: background var(--transition-base);
    }
    .faq-question:hover { background: #F3F4F6; }
    .faq-arrow {
      transition: transform var(--transition-base);
      font-size: 0.8em;
      color: var(--color-text-secondary);
    }
    .faq-item.open .faq-arrow {
      transform: rotate(180deg);
    }
    .faq-answer {
      max-height: 0;
      overflow: hidden;
      transition: max-height 0.4s ease, padding 0.3s ease;
    }
    .faq-item.open .faq-answer {
      max-height: 600px;
      padding: var(--spacing-base) var(--spacing-lg);
    }
    .faq-answer-text {
      font-size: 0.9em;
      color: var(--color-text-secondary);
      line-height: 1.7;
    }

    /* ========================================
       Cheat Sheet
       ======================================== */
    .cheatsheet {
      background: linear-gradient(135deg, var(--color-aws-dark) 0%, #1a2332 100%);
      color: var(--color-text-white);
      border-radius: var(--radius-xl);
      padding: var(--spacing-2xl);
    }
    .cheatsheet h2 {
      font-size: 1.4em;
      margin-bottom: var(--spacing-lg);
      border-bottom: 2px solid var(--color-aws-orange-original);
      padding-bottom: var(--spacing-sm);
      color: var(--color-text-white);
    }
    .cheat-grid {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: var(--spacing-base);
    }
    .cheat-item {
      background: rgba(255,255,255,0.06);
      border: 1px solid rgba(255,255,255,0.1);
      border-radius: var(--radius-base);
      padding: var(--spacing-base);
    }
    .cheat-q {
      font-size: 0.85em;
      color: var(--color-aws-orange-original);
      font-weight: var(--font-weight-semibold);
      margin-bottom: 6px;
    }
    .cheat-a {
      font-size: 0.88em;
      color: rgba(255,255,255,0.85);
      line-height: 1.5;
    }

    /* ========================================
       Scroll-to-Top Button
       ======================================== */
    .scroll-to-top {
      position: fixed;
      bottom: var(--spacing-lg);
      right: var(--spacing-lg);
      width: 50px; height: 50px;
      background: linear-gradient(135deg, var(--color-aws-orange-original) 0%, var(--color-aws-orange-hover) 100%);
      color: var(--color-text-white);
      border: none;
      border-radius: 50%;
      font-size: 1.3em;
      cursor: pointer;
      box-shadow: 0 4px 12px rgba(255,153,0,0.4);
      opacity: 0;
      visibility: hidden;
      transition: all var(--transition-base);
      z-index: 1000;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .scroll-to-top.show { opacity: 1; visibility: visible; }
    .scroll-to-top:hover { transform: translateY(-5px); box-shadow: 0 6px 20px rgba(255,153,0,0.6); }

    /* ========================================
       Responsive
       ======================================== */
    @media (max-width: 768px) {
      body { padding: 10px; padding-top: 70px; font-size: 18px; }
      .takeaway-grid,
      .settings-grid,
      .matrix-grid,
      .practices-grid,
      .usecase-grid,
      .cheat-grid { grid-template-columns: 1fr; }
      .req-conditions {
        grid-template-columns: 1fr;
        text-align: center;
      }
      .req-operator { font-size: 1.4em; }
      .hero { padding: var(--spacing-2xl) var(--spacing-base); }
      .hero h1 { font-size: 1.6em; }
      .section { padding: var(--spacing-base); }
      .fixed-nav-links { display: none; }
    }

    /* ========================================
       Focus & Accessibility
       ======================================== */
    a:focus, button:focus {
      outline: 3px solid var(--color-aws-orange-original);
      outline-offset: 2px;
    }