/* ============================================
   KUBERNETES FROM FIRST PRINCIPLES
   Mission-control / engineering blueprint aesthetic
   ============================================ */

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

:root {
  /* Light theme (default) */
  --bg: #f8f9fb;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f0f2f5;
  --bg-code: #f4f5f7;
  --fg: #1a1d23;
  --fg-secondary: #4a5068;
  --fg-muted: #8892a8;
  --border: #e2e5ec;
  --border-light: #eef0f4;

  /* Kubernetes blue */
  --k8s-blue: #326CE5;
  --k8s-blue-light: #e8f0fe;
  --k8s-blue-dark: #2855b5;

  /* Component semantic colors */
  --color-apiserver: #326CE5;
  --color-etcd: #8B5CF6;
  --color-scheduler: #F59E0B;
  --color-controller: #EA580C;
  --color-ccm: #0D9488;
  --color-kubelet: #16A34A;
  --color-kubeproxy: #DC2626;
  --color-runtime: #6366F1;

  /* Component semantic backgrounds */
  --color-apiserver-bg: #e8f0fe;
  --color-etcd-bg: #f3e8ff;
  --color-scheduler-bg: #fef3c7;
  --color-controller-bg: #fff7ed;
  --color-ccm-bg: #ccfbf1;
  --color-kubelet-bg: #dcfce7;
  --color-kubeproxy-bg: #fee2e2;
  --color-runtime-bg: #e0e7ff;

  /* Status */
  --success: #16A34A;
  --warning: #F59E0B;
  --error: #DC2626;
  --info: #326CE5;

  /* Sizing */
  --sidebar-width: 260px;
  --content-max: 920px;
  --section-gap: 5rem;
  --radius: 10px;
  --radius-sm: 6px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.04);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.12), 0 4px 12px rgba(0,0,0,0.06);

  /* Transitions */
  --transition: 0.2s ease;
  --transition-slow: 0.4s ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1117;
    --bg-secondary: #1a1d27;
    --bg-tertiary: #22252f;
    --bg-code: #1e2230;
    --fg: #e4e7ef;
    --fg-secondary: #a0a8c0;
    --fg-muted: #6b7394;
    --border: #2a2e3a;
    --border-light: #23262f;

    --k8s-blue-light: #1a2744;

    --color-apiserver-bg: #1a2744;
    --color-etcd-bg: #2a1f44;
    --color-scheduler-bg: #2a2210;
    --color-controller-bg: #2a1a10;
    --color-ccm-bg: #0a2a28;
    --color-kubelet-bg: #0a2a14;
    --color-kubeproxy-bg: #2a1010;
    --color-runtime-bg: #1a1a3a;

    --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
    --shadow-lg: 0 12px 40px rgba(0,0,0,0.5);
  }
}

/* --- Typography --- */
html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.7;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  font-weight: 700;
  line-height: 1.25;
  color: var(--fg);
}

h1 { font-size: 2.75rem; letter-spacing: -0.03em; }
h2 { font-size: 2rem; letter-spacing: -0.02em; margin-bottom: 1rem; }
h3 { font-size: 1.4rem; margin-bottom: 0.75rem; }
h4 { font-size: 1.1rem; margin-bottom: 0.5rem; }

p { margin-bottom: 1rem; color: var(--fg-secondary); }

a {
  color: var(--k8s-blue);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: var(--k8s-blue-dark); }

strong { color: var(--fg); font-weight: 600; }
code {
  font-family: 'SF Mono', 'Fira Code', 'JetBrains Mono', 'Cascadia Code', Consolas, monospace;
  font-size: 0.88em;
  background: var(--bg-code);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  color: var(--k8s-blue);
}

/* --- Layout --- */
.page-wrapper {
  display: flex;
  min-height: 100vh;
}

/* --- Sidebar --- */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-secondary);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 100;
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-slow);
}

.sidebar-header {
  padding: 1.5rem 1.25rem 1rem;
  border-bottom: 1px solid var(--border);
}

.sidebar-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--fg);
}

.sidebar-logo .k8s-icon {
  width: 28px;
  height: 28px;
  background: var(--k8s-blue);
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 0.75rem;
  font-weight: 800;
}

.sidebar-nav {
  flex: 1;
  padding: 0.75rem 0;
  overflow-y: auto;
}

.sidebar-nav a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 1.25rem;
  font-size: 0.82rem;
  color: var(--fg-muted);
  transition: all var(--transition);
  border-left: 2px solid transparent;
  text-decoration: none;
  line-height: 1.4;
}

.sidebar-nav a:hover {
  color: var(--fg-secondary);
  background: var(--bg-tertiary);
}

.sidebar-nav a.active {
  color: var(--k8s-blue);
  border-left-color: var(--k8s-blue);
  background: var(--k8s-blue-light);
  font-weight: 600;
}

.sidebar-nav .nav-number {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--fg-muted);
  min-width: 1.2rem;
  opacity: 0.6;
}

.sidebar-nav a.active .nav-number {
  color: var(--k8s-blue);
  opacity: 1;
}

.sidebar-nav .nav-divider {
  height: 1px;
  background: var(--border);
  margin: 0.5rem 1.25rem;
}

/* Mobile hamburger */
.mobile-toggle {
  display: none;
  position: fixed;
  top: 1rem;
  left: 1rem;
  z-index: 200;
  width: 40px;
  height: 40px;
  border-radius: 8px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  cursor: pointer;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  box-shadow: var(--shadow-sm);
}

.mobile-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--fg);
  border-radius: 2px;
  transition: all var(--transition);
}

.mobile-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 90;
}

/* --- Main Content --- */
.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-height: 100vh;
}

.content-inner {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 2rem 2.5rem 6rem;
}

section {
  padding-top: var(--section-gap);
}

section:first-child {
  padding-top: 2rem;
}

.section-label {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--k8s-blue);
  margin-bottom: 0.75rem;
}

.section-label .label-line {
  width: 24px;
  height: 2px;
  background: var(--k8s-blue);
  border-radius: 1px;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--fg-muted);
  margin-bottom: 2.5rem;
  max-width: 640px;
}

/* --- Hero Section --- */
.hero {
  padding: 4rem 0 2rem !important;
  text-align: center;
}

.hero h1 {
  font-size: 3rem;
  letter-spacing: -0.04em;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, var(--k8s-blue), #8B5CF6);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero .hero-subtitle {
  font-size: 1.25rem;
  color: var(--fg-secondary);
  max-width: 600px;
  margin: 0 auto 2.5rem;
  line-height: 1.6;
}

.hero-visual {
  max-width: 760px;
  margin: 0 auto;
  padding: 2rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}

/* --- Component Cards --- */
.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1rem;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--k8s-blue);
}

.card-colored {
  border-left: 3px solid var(--card-color, var(--k8s-blue));
}

.card h4 {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.card .card-icon {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 700;
  color: white;
  flex-shrink: 0;
}

/* --- Concept Grid --- */
.concept-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}

.concept-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: all var(--transition);
}

.concept-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.concept-card .concept-icon {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  margin-bottom: 0.75rem;
  font-weight: 700;
}

.concept-card h4 {
  font-size: 1rem;
  margin-bottom: 0.4rem;
}

.concept-card p {
  font-size: 0.88rem;
  margin-bottom: 0;
  color: var(--fg-muted);
}

/* --- Callout Boxes --- */
.callout {
  padding: 1.25rem 1.5rem;
  border-radius: var(--radius);
  margin: 1.5rem 0;
  border-left: 3px solid;
  font-size: 0.92rem;
}

.callout-insight {
  background: var(--k8s-blue-light);
  border-color: var(--k8s-blue);
}

.callout-insight .callout-title { color: var(--k8s-blue); }

.callout-warning {
  background: var(--color-scheduler-bg);
  border-color: var(--warning);
}

.callout-warning .callout-title { color: var(--warning); }

.callout-title {
  font-weight: 700;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.35rem;
}

.callout p {
  margin-bottom: 0;
  color: var(--fg-secondary);
}

/* --- Code Blocks --- */
.code-block {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin: 1.5rem 0;
  overflow: hidden;
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.5rem 1rem;
  background: var(--bg-tertiary);
  border-bottom: 1px solid var(--border);
  font-size: 0.78rem;
  color: var(--fg-muted);
  font-weight: 600;
}

.code-header .lang-badge {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.1rem 0.5rem;
  border-radius: 4px;
  background: var(--k8s-blue-light);
  color: var(--k8s-blue);
}

.code-body {
  padding: 1rem 1.25rem;
  overflow-x: auto;
  font-family: 'SF Mono', 'Fira Code', 'JetBrains Mono', Consolas, monospace;
  font-size: 0.82rem;
  line-height: 1.65;
  color: var(--fg);
  white-space: pre;
  tab-size: 2;
}

.code-body .kw { color: #c678dd; }
.code-body .fn { color: #61afef; }
.code-body .str { color: #98c379; }
.code-body .cm { color: var(--fg-muted); font-style: italic; }
.code-body .num { color: #d19a66; }
.code-body .type { color: #e5c07b; }
.code-body .op { color: #56b6c2; }

@media (prefers-color-scheme: light) {
  .code-body .kw { color: #a626a4; }
  .code-body .fn { color: #4078f2; }
  .code-body .str { color: #50a14f; }
  .code-body .num { color: #986801; }
  .code-body .type { color: #c18401; }
  .code-body .op { color: #0184bc; }
}

/* --- Architecture Diagrams --- */
.diagram-container {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  margin: 2rem 0;
  box-shadow: var(--shadow-sm);
  overflow-x: auto;
}

.diagram-title {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-muted);
  text-align: center;
  margin-bottom: 1.5rem;
}

/* Diagram components */
.d-box {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-sm);
  border: 2px solid;
  font-size: 0.8rem;
  font-weight: 600;
  text-align: center;
  transition: all var(--transition);
  position: relative;
  min-width: 100px;
}

.d-box.active {
  transform: scale(1.05);
  box-shadow: var(--shadow-md);
  z-index: 2;
}

.d-box.dimmed {
  opacity: 0.3;
  transform: scale(0.98);
}

.d-box-label {
  font-size: 0.68rem;
  color: var(--fg-muted);
  margin-top: 0.2rem;
  font-weight: 400;
}

/* Themed boxes */
.d-box-apiserver { border-color: var(--color-apiserver); background: var(--color-apiserver-bg); color: var(--color-apiserver); }
.d-box-etcd { border-color: var(--color-etcd); background: var(--color-etcd-bg); color: var(--color-etcd); }
.d-box-scheduler { border-color: var(--color-scheduler); background: var(--color-scheduler-bg); color: var(--color-scheduler); }
.d-box-controller { border-color: var(--color-controller); background: var(--color-controller-bg); color: var(--color-controller); }
.d-box-ccm { border-color: var(--color-ccm); background: var(--color-ccm-bg); color: var(--color-ccm); }
.d-box-kubelet { border-color: var(--color-kubelet); background: var(--color-kubelet-bg); color: var(--color-kubelet); }
.d-box-kubeproxy { border-color: var(--color-kubeproxy); background: var(--color-kubeproxy-bg); color: var(--color-kubeproxy); }
.d-box-runtime { border-color: var(--color-runtime); background: var(--color-runtime-bg); color: var(--color-runtime); }
.d-box-neutral { border-color: var(--border); background: var(--bg-tertiary); color: var(--fg-secondary); }
.d-box-cloud { border-color: var(--color-ccm); background: var(--color-ccm-bg); color: var(--color-ccm); border-style: dashed; }

/* Arrows */
.d-arrow-right {
  display: flex;
  align-items: center;
  padding: 0 0.4rem;
  color: var(--fg-muted);
  font-size: 1rem;
  transition: all var(--transition);
}

.d-arrow-right.active { color: var(--k8s-blue); }
.d-arrow-right.dimmed { opacity: 0.2; }

.d-arrow-down {
  display: flex;
  justify-content: center;
  padding: 0.3rem 0;
  color: var(--fg-muted);
  font-size: 1rem;
  transition: all var(--transition);
}

.d-arrow-down.active { color: var(--k8s-blue); }
.d-arrow-down.dimmed { opacity: 0.2; }

.d-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  flex-wrap: wrap;
}

.d-col {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.d-group {
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 1rem;
  position: relative;
}

.d-group-label {
  position: absolute;
  top: -0.6rem;
  left: 1rem;
  background: var(--bg-secondary);
  padding: 0 0.5rem;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-muted);
}

/* --- Flow Diagram (Animated) --- */
.flow-container {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin: 2rem 0;
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.flow-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.5rem;
  background: var(--bg-tertiary);
  border-bottom: 1px solid var(--border);
}

.flow-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--fg);
}

.flow-controls {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.flow-btn {
  width: 32px;
  height: 32px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  color: var(--fg);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  transition: all var(--transition);
}

.flow-btn:hover {
  background: var(--k8s-blue);
  color: white;
  border-color: var(--k8s-blue);
}

.flow-btn:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

.flow-btn:disabled:hover {
  background: var(--bg-secondary);
  color: var(--fg);
  border-color: var(--border);
}

.flow-step-indicator {
  display: flex;
  gap: 4px;
  margin: 0 0.5rem;
}

.flow-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--border);
  transition: all var(--transition);
}

.flow-dot.active {
  background: var(--k8s-blue);
  transform: scale(1.3);
}

.flow-dot.completed {
  background: var(--success);
}

.flow-diagram-area {
  padding: 2rem;
  min-height: 200px;
}

.flow-description {
  padding: 1rem 1.5rem;
  border-top: 1px solid var(--border);
  background: var(--bg-tertiary);
}

.flow-step-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--k8s-blue);
  color: white;
  font-size: 0.7rem;
  font-weight: 700;
  margin-right: 0.5rem;
  flex-shrink: 0;
}

.flow-step-text {
  font-size: 0.9rem;
  color: var(--fg-secondary);
  line-height: 1.5;
}

.flow-step-text strong {
  color: var(--fg);
}

/* --- Timeline / Process Steps --- */
.process-steps {
  position: relative;
  margin: 2rem 0;
  padding-left: 2rem;
}

.process-steps::before {
  content: '';
  position: absolute;
  left: 0.55rem;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--border);
}

.process-step {
  position: relative;
  margin-bottom: 1.5rem;
  padding-left: 1rem;
}

.process-step::before {
  content: attr(data-step);
  position: absolute;
  left: -2rem;
  top: 0.15rem;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--k8s-blue);
  color: white;
  font-size: 0.7rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.process-step h4 {
  font-size: 0.95rem;
  margin-bottom: 0.3rem;
}

.process-step p {
  font-size: 0.88rem;
  margin-bottom: 0;
}

/* --- Comparison / Before-After --- */
.comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin: 2rem 0;
}

.comparison-side {
  padding: 1.5rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
}

.comparison-side.before {
  border-color: var(--error);
  background: var(--color-kubeproxy-bg);
}

.comparison-side.after {
  border-color: var(--success);
  background: var(--color-kubelet-bg);
}

.comparison-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.75rem;
}

.comparison-side.before .comparison-label { color: var(--error); }
.comparison-side.after .comparison-label { color: var(--success); }

.comparison-side ul {
  list-style: none;
  padding: 0;
}

.comparison-side li {
  font-size: 0.88rem;
  color: var(--fg-secondary);
  padding: 0.25rem 0;
  padding-left: 1.25rem;
  position: relative;
}

.comparison-side.before li::before {
  content: '✕';
  position: absolute;
  left: 0;
  color: var(--error);
  font-weight: 700;
  font-size: 0.75rem;
}

.comparison-side.after li::before {
  content: '✓';
  position: absolute;
  left: 0;
  color: var(--success);
  font-weight: 700;
  font-size: 0.75rem;
}

/* --- Table --- */
.styled-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.88rem;
}

.styled-table th {
  background: var(--bg-tertiary);
  padding: 0.75rem 1rem;
  text-align: left;
  font-weight: 700;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--fg-muted);
  border-bottom: 2px solid var(--border);
}

.styled-table td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-light);
  color: var(--fg-secondary);
}

.styled-table tr:hover td {
  background: var(--bg-tertiary);
}

/* --- Subsection spacing --- */
.subsection {
  margin-top: 3rem;
}

.subsection:first-child {
  margin-top: 0;
}

/* --- Content lists --- */
.content-list {
  list-style: none;
  padding: 0;
  margin: 1rem 0;
}

.content-list li {
  position: relative;
  padding: 0.35rem 0 0.35rem 1.5rem;
  color: var(--fg-secondary);
  font-size: 0.92rem;
}

.content-list li::before {
  content: '→';
  position: absolute;
  left: 0;
  color: var(--k8s-blue);
  font-weight: 600;
}

/* --- Tags / Badges --- */
.tag {
  display: inline-block;
  padding: 0.15rem 0.6rem;
  border-radius: 4px;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.tag-blue { background: var(--color-apiserver-bg); color: var(--color-apiserver); }
.tag-purple { background: var(--color-etcd-bg); color: var(--color-etcd); }
.tag-green { background: var(--color-kubelet-bg); color: var(--color-kubelet); }
.tag-amber { background: var(--color-scheduler-bg); color: var(--color-scheduler); }
.tag-teal { background: var(--color-ccm-bg); color: var(--color-ccm); }
.tag-orange { background: var(--color-controller-bg); color: var(--color-controller); }

/* --- Reveal animations --- */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- Pulse animation for active flow components --- */
@keyframes pulse-glow {
  0%, 100% { box-shadow: 0 0 0 0 rgba(50, 108, 229, 0.3); }
  50% { box-shadow: 0 0 0 8px rgba(50, 108, 229, 0); }
}

.d-box.active {
  animation: pulse-glow 2s infinite;
}

@keyframes data-flow {
  0% { background-position: 0% 50%; }
  100% { background-position: 100% 50%; }
}

.d-arrow-right.active::after {
  content: '';
  display: inline-block;
  width: 20px;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--k8s-blue), transparent);
  background-size: 200% 100%;
  animation: data-flow 1s linear infinite;
}

/* --- Hero cluster animation --- */
.hero-cluster {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  align-items: stretch;
}

.hero-node {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
  min-width: 140px;
  position: relative;
}

.hero-node-title {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-muted);
  margin-bottom: 0.75rem;
  text-align: center;
}

.hero-pods {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  justify-content: center;
}

.hero-pod {
  width: 28px;
  height: 28px;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.6rem;
  font-weight: 700;
  color: white;
  transition: all 0.5s ease;
}

@keyframes pod-appear {
  0% { transform: scale(0); opacity: 0; }
  50% { transform: scale(1.2); }
  100% { transform: scale(1); opacity: 1; }
}

.hero-pod.animate {
  animation: pod-appear 0.5s ease forwards;
}

/* Control plane section in hero */
.hero-cp {
  text-align: center;
  margin-bottom: 1.5rem;
}

.hero-cp-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--k8s-blue);
  margin-bottom: 0.75rem;
}

.hero-cp-boxes {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
  flex-wrap: wrap;
}

.hero-cp-box {
  padding: 0.4rem 0.8rem;
  border-radius: 5px;
  font-size: 0.7rem;
  font-weight: 600;
  border: 1px solid;
}

.hero-connector {
  display: flex;
  justify-content: center;
  padding: 0.5rem 0;
  color: var(--fg-muted);
  font-size: 0.85rem;
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .mobile-toggle {
    display: flex;
  }

  .sidebar {
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .mobile-overlay.open {
    display: block;
  }

  .main-content {
    margin-left: 0;
  }

  .content-inner {
    padding: 4rem 1.25rem 4rem;
  }

  .hero h1 {
    font-size: 2rem;
  }

  h2 { font-size: 1.5rem; }

  .concept-grid {
    grid-template-columns: 1fr;
  }

  .comparison {
    grid-template-columns: 1fr;
  }

  .d-row {
    flex-direction: column;
  }

  .d-arrow-right {
    transform: rotate(90deg);
  }

  .hero-cluster {
    flex-direction: column;
    align-items: center;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 1.6rem;
  }

  .content-inner {
    padding: 4rem 1rem 3rem;
  }

  .flow-diagram-area {
    padding: 1rem;
  }
}

/* --- Architecture diagram specific layouts --- */
.arch-diagram {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
}

.arch-plane {
  width: 100%;
  padding: 1.25rem;
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  position: relative;
}

.arch-plane-label {
  position: absolute;
  top: -0.6rem;
  left: 1rem;
  background: var(--bg-secondary);
  padding: 0 0.5rem;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-muted);
}

.arch-components {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  flex-wrap: wrap;
}

.arch-connector {
  display: flex;
  justify-content: center;
  color: var(--fg-muted);
  font-size: 1.2rem;
  padding: 0.25rem 0;
}

/* Node diagram for data plane */
.node-diagram {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.node-box {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
  min-width: 180px;
  background: var(--bg-tertiary);
}

.node-box-title {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-muted);
  margin-bottom: 0.75rem;
  text-align: center;
}

.node-component {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.5rem;
  border-radius: 4px;
  font-size: 0.78rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

/* --- Controller loop animation --- */
.reconcile-loop {
  display: flex;
  align-items: center;
  gap: 1rem;
  justify-content: center;
  margin: 1.5rem 0;
  flex-wrap: wrap;
}

.reconcile-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.3rem;
  padding: 0.75rem 1rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-secondary);
  min-width: 90px;
  text-align: center;
  transition: all var(--transition);
}

.reconcile-step.active {
  border-color: var(--k8s-blue);
  background: var(--k8s-blue-light);
  transform: scale(1.08);
}

.reconcile-step-icon {
  font-size: 1.2rem;
}

.reconcile-step-label {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--fg-secondary);
}

.reconcile-arrow {
  color: var(--fg-muted);
  font-size: 1rem;
}

/* --- Footer --- */
.site-footer {
  text-align: center;
  padding: 3rem 0;
  border-top: 1px solid var(--border);
  margin-top: 4rem;
  color: var(--fg-muted);
  font-size: 0.82rem;
}

/* Scroll margin for anchor links */
section[id] {
  scroll-margin-top: 2rem;
}

/* Print styles */
@media print {
  .sidebar, .mobile-toggle, .flow-controls { display: none !important; }
  .main-content { margin-left: 0 !important; }
  .d-box { border-width: 1px !important; }
}