/* ============================================================
   DGX Spark Ebook — Responsive Stylesheet
   Color theme: serverlessvc.com (light, green, glassmorphism)
   ============================================================ */

:root {
  /* ── serverlessvc.com palette ── */
  --color-bg: #ffffff;
  --color-bg-gradient: linear-gradient(135deg, #e8f5f0 0%, #dceefb 30%, #f0f4ff 60%, #faf0fb 100%);
  --color-surface: rgba(255, 255, 255, 0.65);
  --color-surface-solid: #ffffff;
  --color-surface-2: #f0f9f4;       /* green-50 */
  --color-border: rgba(209, 250, 229, 0.8);  /* green-100 glass */
  --color-border-solid: #d1fae5;    /* green-100 */
  --color-accent: #1e7350;          /* serverlessvc custom green-600 */
  --color-accent-hover: #185c40;    /* serverlessvc custom green-700 */
  --color-accent-light: #dcf0e6;    /* serverlessvc custom green-100 */
  --color-accent-xlight: #f0f9f4;   /* serverlessvc custom green-50 */
  --color-accent-2: #3b82f6;        /* blue for secondary links */
  --color-text: #374151;            /* gray-700 */
  --color-text-muted: #6b7280;      /* gray-500 */
  --color-heading: #1f2937;         /* gray-800 */
  --color-code-bg: #f9fafb;         /* gray-50 */
  --color-code-border: #e5e7eb;     /* gray-200 */
  --color-code-text: #1e7350;       /* green accent for inline code */
  --sidebar-width: 280px;
  --content-max: 860px;
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
  --radius: 8px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.06), 0 1px 4px rgba(0,0,0,0.04);
  --shadow-card-hover: 0 20px 60px rgba(0, 0, 0, 0.1);
  --transition: 0.2s ease;
}

/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }

body {
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

/* ── Skip link (accessibility) ── */
.skip-link {
  position: absolute;
  left: -9999px;
  top: auto;
  background: var(--color-accent);
  color: #fff;
  padding: 8px 16px;
  z-index: 9999;
  border-radius: 0 0 var(--radius) 0;
  font-weight: 600;
}
.skip-link:focus { left: 0; }

/* ── Layout ── */
.layout {
  display: flex;
  min-height: 100vh;
}

/* ── Sidebar ── */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-right: 1px solid var(--color-border-solid);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  z-index: 100;
  transition: transform var(--transition);
}

.sidebar-header {
  padding: 20px 20px 16px;
  border-bottom: 1px solid var(--color-border-solid);
  flex-shrink: 0;
  background: rgba(240, 249, 244, 0.6);
}

.sidebar-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}

.sidebar-logo .logo-badge {
  background: var(--color-accent);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 100px;
  letter-spacing: 0.5px;
  flex-shrink: 0;
}

.sidebar-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-heading);
  line-height: 1.4;
}

.sidebar-meta {
  font-size: 11px;
  color: var(--color-text-muted);
  margin-top: 4px;
}

.sidebar-nav {
  overflow-y: auto;
  flex: 1;
  padding: 12px 0 20px;
  scrollbar-width: thin;
  scrollbar-color: var(--color-border-solid) transparent;
}

.sidebar-nav::-webkit-scrollbar { width: 4px; }
.sidebar-nav::-webkit-scrollbar-track { background: transparent; }
.sidebar-nav::-webkit-scrollbar-thumb { background: var(--color-border-solid); border-radius: 2px; }

.nav-section-label {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--color-text-muted);
  padding: 16px 20px 6px;
}

.nav-item {
  display: block;
  padding: 7px 20px;
  font-size: 13px;
  color: var(--color-text-muted);
  text-decoration: none;
  border-left: 2px solid transparent;
  transition: all var(--transition);
  line-height: 1.4;
}

.nav-item:hover {
  color: var(--color-accent);
  background: var(--color-accent-xlight);
  border-left-color: var(--color-accent-light);
  text-decoration: none;
}

.nav-item.active {
  color: var(--color-accent);
  border-left-color: var(--color-accent);
  background: var(--color-accent-xlight);
  font-weight: 500;
}

.nav-item.nav-sub {
  padding-left: 32px;
  font-size: 12px;
}

/* ── Main content ── */
.main {
  margin-left: var(--sidebar-width);
  flex: 1;
  min-width: 0;
  background: var(--color-bg);
}

/* ── Top bar ── */
.topbar {
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-solid);
  padding: 0 40px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  z-index: 50;
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--color-text);
  cursor: pointer;
  padding: 6px;
  border-radius: var(--radius);
}

.menu-toggle:hover { background: var(--color-surface-2); }

.breadcrumb {
  font-size: 13px;
  color: var(--color-text-muted);
  display: flex;
  align-items: center;
  gap: 6px;
}

.breadcrumb span { color: var(--color-heading); font-weight: 500; }

.topbar-right {
  display: flex;
  align-items: center;
  gap: 10px;
}

.btn-download {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--color-accent);
  color: #fff;
  font-size: 12px;
  font-weight: 600;
  padding: 7px 16px;
  border-radius: 100px;
  text-decoration: none;
  transition: background var(--transition), opacity var(--transition);
}

.btn-download:hover { background: var(--color-accent-hover); text-decoration: none; }

/* ── Animated gradient orbs (serverlessvc.com style) ── */
.gradient-bg {
  position: relative;
  background: var(--color-bg-gradient);
  background-size: 400% 400%;
  animation: gradientShift 18s ease infinite;
  overflow: hidden;
}

@keyframes gradientShift {
  0%, 100% { background-position: 0% 50%; }
  50%       { background-position: 100% 50%; }
}

.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(60px);
  opacity: 0.5;
  pointer-events: none;
}

/* ── Cover section ── */
.cover-section {
  border-bottom: 1px solid var(--color-border-solid);
  padding: 88px 40px 80px;
  text-align: center;
}

.cover-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.75);
  backdrop-filter: blur(8px);
  border: 1px solid var(--color-border-solid);
  color: var(--color-accent);
  font-size: 12px;
  font-weight: 600;
  padding: 7px 16px;
  border-radius: 100px;
  margin-bottom: 28px;
  letter-spacing: 0.3px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}

.cover-title {
  font-size: clamp(28px, 5vw, 52px);
  font-weight: 300;
  color: var(--color-heading);
  line-height: 1.15;
  margin-bottom: 16px;
  letter-spacing: -0.5px;
}

.cover-title em {
  font-style: normal;
  font-weight: 700;
  color: var(--color-accent);
}

.cover-subtitle {
  font-size: clamp(15px, 2vw, 20px);
  color: var(--color-text-muted);
  max-width: 620px;
  margin: 0 auto 32px;
  line-height: 1.65;
  font-weight: 300;
}

.cover-authors {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 14px;
  color: var(--color-text-muted);
  margin-bottom: 40px;
}

.cover-authors strong { color: var(--color-heading); font-weight: 600; }
.cover-authors a { color: var(--color-accent); text-decoration: none; font-weight: 500; }
.cover-authors a:hover { text-decoration: underline; }

.cover-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 40px;
  flex-wrap: wrap;
}

.stat-item { text-align: center; }

.stat-value {
  display: block;
  font-size: 26px;
  font-weight: 700;
  color: var(--color-accent);
  line-height: 1;
}

.stat-label {
  display: block;
  font-size: 11px;
  color: var(--color-text-muted);
  margin-top: 4px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* ── Content area ── */
.content-area {
  max-width: calc(var(--content-max) + 80px);
  margin: 0 auto;
  padding: 0 40px 80px;
}

/* ── Chapter sections ── */
.chapter-section {
  padding-top: 64px;
}

.chapter-label {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--color-accent);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.chapter-label::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--color-border-solid);
  max-width: 120px;
}

/* ── Typography ── */
h1, h2, h3, h4 {
  color: var(--color-heading);
  line-height: 1.3;
  font-weight: 700;
}

h1 { font-size: clamp(22px, 3vw, 32px); margin-bottom: 12px; font-weight: 700; }
h2 {
  font-size: clamp(17px, 2.5vw, 22px);
  margin: 48px 0 14px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--color-border-solid);
  font-weight: 600;
}
h3 { font-size: 17px; margin: 28px 0 10px; font-weight: 600; }
h4 { font-size: 15px; margin: 20px 0 8px; color: var(--color-text-muted); font-weight: 600; }

p { margin-bottom: 16px; color: var(--color-text); }

a { color: var(--color-accent); text-decoration: none; }
a:hover { text-decoration: underline; }

ul, ol {
  padding-left: 24px;
  margin-bottom: 16px;
}

li { margin-bottom: 6px; color: var(--color-text); }

strong { color: var(--color-heading); font-weight: 600; }
em { color: var(--color-text); }

hr {
  border: none;
  border-top: 1px solid var(--color-border-solid);
  margin: 40px 0;
}

/* ── Code blocks ── */
pre {
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-lg);
  padding: 20px 24px;
  overflow-x: auto;
  margin: 20px 0;
}

pre code {
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.65;
  color: #1f2937;
  background: none;
  border: none;
  padding: 0;
}

code {
  font-family: var(--font-mono);
  font-size: 13px;
  background: var(--color-accent-xlight);
  border: 1px solid var(--color-accent-light);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--color-accent);
}

/* ── Tables ── */
.table-wrapper { overflow-x: auto; margin: 20px 0; }

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  background: var(--color-surface-solid);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-card);
}

th {
  background: var(--color-surface-2);
  color: var(--color-text-muted);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--color-border-solid);
}

td {
  padding: 11px 16px;
  border-bottom: 1px solid #f3f4f6;
  vertical-align: top;
  color: var(--color-text);
}

tr:last-child td { border-bottom: none; }
tr:hover td { background: var(--color-accent-xlight); }
td code { font-size: 12px; }

/* ── Callout boxes ── */
.callout {
  border-left: 3px solid;
  padding: 14px 18px;
  border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
  margin: 20px 0;
  font-size: 14px;
  line-height: 1.65;
}

.callout-note {
  border-color: var(--color-accent-2);
  background: #eff6ff;
}

.callout-warning {
  border-color: #f59e0b;
  background: #fffbeb;
}

.callout-critical {
  border-color: #ef4444;
  background: #fef2f2;
}

.callout-title {
  font-weight: 700;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 6px;
}

.callout-note .callout-title    { color: var(--color-accent-2); }
.callout-warning .callout-title { color: #d97706; }
.callout-critical .callout-title { color: #dc2626; }

blockquote {
  border-left: 3px solid var(--color-accent-light);
  padding: 12px 18px;
  margin: 16px 0;
  color: var(--color-text-muted);
  background: var(--color-accent-xlight);
  border-radius: 0 var(--radius) var(--radius) 0;
}

blockquote strong { color: var(--color-heading); }

/* ── Architecture diagrams ── */
.arch-diagram {
  background: var(--color-code-bg);
  border: 1px solid var(--color-code-border);
  border-radius: var(--radius-lg);
  padding: 20px;
  overflow-x: auto;
  margin: 20px 0;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.65;
  color: var(--color-text-muted);
  white-space: pre;
}

/* ── Stack cards (glassmorphism, serverlessvc style) ── */
.stack-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.stack-card {
  background: var(--color-surface);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.8);
  border-radius: var(--radius-xl);
  padding: 24px;
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition), transform var(--transition);
}

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

.stack-card-icon {
  font-size: 26px;
  margin-bottom: 12px;
  display: block;
}

.stack-card-name {
  font-size: 15px;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 6px;
}

.stack-card-desc {
  font-size: 13px;
  color: var(--color-text-muted);
  line-height: 1.55;
}

.stack-card-version {
  display: inline-block;
  margin-top: 12px;
  font-size: 11px;
  background: var(--color-accent-xlight);
  border: 1px solid var(--color-accent-light);
  padding: 3px 10px;
  border-radius: 100px;
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-weight: 500;
}

/* ── Chapter navigation ── */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 64px;
  padding-top: 32px;
  border-top: 1px solid var(--color-border-solid);
}

.chapter-nav-btn {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 22px;
  background: var(--color-surface);
  backdrop-filter: blur(8px);
  border: 1px solid var(--color-border-solid);
  border-radius: var(--radius-xl);
  text-decoration: none;
  color: var(--color-heading);
  font-size: 14px;
  box-shadow: var(--shadow-card);
  transition: all var(--transition);
  max-width: 280px;
  font-weight: 500;
}

.chapter-nav-btn:hover {
  border-color: var(--color-accent);
  background: var(--color-accent-xlight);
  box-shadow: 0 4px 16px rgba(30, 115, 80, 0.12);
  text-decoration: none;
  color: var(--color-accent);
}

.nav-btn-label {
  font-size: 11px;
  color: var(--color-text-muted);
  display: block;
  margin-bottom: 2px;
  font-weight: 400;
}

.nav-btn-title { font-weight: 600; font-size: 13px; }
.chapter-nav-btn.next { margin-left: auto; text-align: right; }

/* ── FAQ / AEO section ── */
.faq-section { margin: 64px 0; }

.faq-title {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 28px;
  color: var(--color-heading);
}

.faq-item {
  border: 1px solid var(--color-border-solid);
  border-radius: var(--radius-lg);
  margin-bottom: 10px;
  overflow: hidden;
  background: var(--color-surface-solid);
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition);
}

.faq-item:hover { box-shadow: 0 8px 24px rgba(0,0,0,0.08); }

.faq-question {
  padding: 16px 20px;
  font-weight: 600;
  font-size: 15px;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--color-heading);
  background: var(--color-surface-solid);
  transition: background var(--transition), color var(--transition);
  list-style: none;
}

.faq-question::-webkit-details-marker { display: none; }
.faq-question:hover { background: var(--color-accent-xlight); color: var(--color-accent); }
details[open] .faq-question {
  border-bottom: 1px solid var(--color-border-solid);
  color: var(--color-accent);
  background: var(--color-accent-xlight);
}

.faq-chevron {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  transition: transform var(--transition);
  color: var(--color-text-muted);
  stroke: currentColor;
  fill: none;
}

details[open] .faq-chevron { transform: rotate(180deg); color: var(--color-accent); }

.faq-answer {
  padding: 18px 20px;
  font-size: 14px;
  color: var(--color-text);
  line-height: 1.75;
  background: #fafafa;
}

.faq-answer code { font-size: 12px; }
.faq-answer pre { margin: 12px 0 0; }

/* ── Sidebar overlay (mobile) ── */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.3);
  z-index: 99;
  backdrop-filter: blur(2px);
}

/* ── Footer ── */
footer {
  background: var(--color-surface-2);
  border-top: 1px solid var(--color-border-solid);
  padding: 32px 40px;
  text-align: center;
  font-size: 13px;
  color: var(--color-text-muted);
}

footer a { color: var(--color-accent); }
footer a:hover { text-decoration: underline; }

/* ── Responsive ── */
@media (max-width: 1024px) {
  :root { --sidebar-width: 260px; }
}

@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); }
  .sidebar-overlay.open { display: block; }
  .menu-toggle { display: flex; }
  .main { margin-left: 0; }
  .topbar { padding: 0 20px; }
  .content-area { padding: 0 20px 60px; }
  .cover-section { padding: 52px 20px 48px; }
  .cover-stats { gap: 24px; }
  .chapter-nav { flex-direction: column; }
  .chapter-nav-btn { max-width: 100%; }
  .chapter-nav-btn.next { margin-left: 0; text-align: left; }
  .stack-grid { grid-template-columns: 1fr; }
  pre { padding: 14px; }
  h2 { font-size: 18px; }
}

@media (max-width: 480px) {
  .cover-title { font-size: 26px; }
  .topbar { height: 48px; }
  .breadcrumb { display: none; }
  .btn-download span { display: none; }
}

/* ── Print ── */
@media print {
  /* Hide web chrome */
  .sidebar, .sidebar-overlay, .topbar, .skip-link,
  .btn-download, .chapter-nav, footer { display: none !important; }

  /* Layout */
  .main { margin-left: 0 !important; }
  .layout { display: block; }
  .content-area { max-width: 100%; padding: 0 0 16px !important; }

  /* Cover */
  .cover-section { padding: 40px 20px 32px !important; min-height: 0 !important; }
  .gradient-bg { background: #f0fdf4 !important; animation: none !important; }
  .orb { display: none !important; }

  /* Compact spacing */
  .chapter-section { padding-top: 4px !important; }
  h1 { font-size: 20pt !important; margin-bottom: 8px !important; }
  h2 { font-size: 14pt !important; margin: 16px 0 8px !important; padding-bottom: 4px !important;
       page-break-before: avoid !important; break-before: avoid !important; }
  h3 { font-size: 12pt !important; margin: 12px 0 6px !important; }
  p  { margin-bottom: 8px !important; }

  /* Never break after a heading */
  h1, h2, h3 { page-break-after: avoid; break-after: avoid; }

  /* Code */
  pre { font-size: 9pt !important; line-height: 1.4 !important;
        padding: 10px 14px !important; margin: 8px 0 !important;
        page-break-inside: avoid; break-inside: avoid;
        white-space: pre-wrap; word-break: break-word; }

  /* Tables */
  table { font-size: 10pt !important; box-shadow: none !important; page-break-inside: avoid; }
  th, td { padding: 6px 10px !important; }

  /* Cards */
  .stack-grid { grid-template-columns: 1fr 1fr !important; gap: 8px !important; }
  .stack-card { box-shadow: none !important; padding: 12px !important; break-inside: avoid; }

  /* Callouts */
  .callout { margin: 8px 0 !important; page-break-inside: avoid; }

  /* FAQ: show all answers */
  .faq-answer { display: block !important; }
  .faq-chevron { display: none !important; }

  /* Figures */
  figure { page-break-inside: avoid; margin: 10px 0 !important; }
  figure svg { max-width: 100% !important; }

  /* Preserve colors */
  * { -webkit-print-color-adjust: exact !important; print-color-adjust: exact !important; }
}