/* =====================================================================
   LMS & EdTech Data Pipelines — global stylesheet
   Light, elegant, easy-on-the-eyes palette designed for long-form
   technical reading on desktop and mobile.
   ===================================================================== */

:root {
  /* Palette */
  --c-ink: #1a2238;
  --c-ink-soft: #3a4a6b;
  --c-muted: #66728f;
  --c-line: #dde3ee;
  --c-line-soft: #eaeef6;
  --c-bg: #f7f9fc;
  --c-surface: #ffffff;
  --c-surface-2: #f1f5fb;
  --c-primary: #2c5fb3;
  --c-primary-strong: #1f3c88;
  --c-primary-tint: #e6efff;
  --c-accent: #00b4a6;
  --c-accent-strong: #008f86;
  --c-accent-tint: #def7f3;
  --c-warm: #ef8354;
  --c-warm-strong: #c95d2a;
  --c-warm-tint: #ffe9dd;
  --c-gold: #ffd166;
  --c-gold-strong: #d9a82f;
  --c-code-bg: #f3f6fb;
  --c-code-ink: #1f2a44;
  --c-code-keyword: #1f3c88;
  --c-code-string: #008f86;
  --c-code-number: #c95d2a;
  --c-code-comment: #7a89a8;

  /* Typography */
  --ff-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --ff-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  /* Layout */
  --container-max: 1380px;
  --container-pad: clamp(1rem, 3vw, 2.25rem);
  --radius: 14px;
  --radius-sm: 8px;
  --header-h: 68px;
  --shadow-1: 0 1px 2px rgba(20, 30, 60, 0.04), 0 4px 16px rgba(20, 30, 60, 0.06);
  --shadow-2: 0 6px 28px rgba(20, 30, 60, 0.12);
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 16px);
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: var(--ff-sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--c-ink);
  background: var(--c-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.site-main { flex: 1 0 auto; }

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

/* Safe default size for inline icon SVGs so they never balloon to the SVG
   user-agent default of 300×150. Specific contexts (nav, cta, card) override. */
.icon { width: 20px; height: 20px; flex-shrink: 0; }

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding-inline: var(--container-pad);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--c-primary);
  color: #fff;
  padding: 0.5rem 0.85rem;
  border-radius: 0 0 8px 0;
  z-index: 1000;
}
.skip-link:focus { left: 0; }

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.86);
  backdrop-filter: saturate(180%) blur(10px);
  -webkit-backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--c-line);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.25rem;
  min-height: var(--header-h);
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  text-decoration: none;
  color: var(--c-ink);
  flex-shrink: 0;
}
.brand-logo { width: 40px; height: 40px; filter: drop-shadow(0 1px 2px rgba(20,30,60,0.12)); }
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-title {
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: -0.01em;
  background: linear-gradient(135deg, var(--c-primary-strong), var(--c-accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.brand-sub { font-size: 0.74rem; color: var(--c-muted); letter-spacing: 0.04em; }

.primary-nav ul {
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.35rem;
  margin: 0;
  padding: 0;
}
.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.55rem 0.85rem;
  border-radius: 999px;
  text-decoration: none;
  color: var(--c-ink-soft);
  font-weight: 500;
  font-size: 0.94rem;
  transition: background 160ms ease, color 160ms ease, transform 160ms ease;
}
.nav-link:hover,
.nav-link:focus-visible {
  background: var(--c-primary-tint);
  color: var(--c-primary-strong);
  transform: translateY(-1px);
}
.nav-link.is-active {
  background: linear-gradient(135deg, var(--c-primary), var(--c-accent));
  color: #fff;
  box-shadow: var(--shadow-1);
}
.nav-link.is-active:hover { color: #fff; }
.nav-icon { display: inline-flex; }
.nav-icon .icon { width: 18px; height: 18px; }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--c-line);
  border-radius: 10px;
  padding: 0.35rem 0.55rem;
  color: var(--c-ink-soft);
  cursor: pointer;
}
.nav-toggle .icon { width: 22px; height: 22px; }
.nav-toggle .nav-toggle-close { display: none; }
.nav-toggle[aria-expanded="true"] .nav-toggle-open { display: none; }
.nav-toggle[aria-expanded="true"] .nav-toggle-close { display: inline-flex; }

@media (max-width: 880px) {
  .nav-toggle { display: inline-flex; align-items: center; }
  .primary-nav {
    position: absolute;
    inset: var(--header-h) 0 auto 0;
    background: var(--c-surface);
    border-bottom: 1px solid var(--c-line);
    box-shadow: var(--shadow-1);
    transform: translateY(-8px);
    opacity: 0;
    pointer-events: none;
    transition: transform 180ms ease, opacity 180ms ease;
  }
  .primary-nav.is-open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .primary-nav ul {
    flex-direction: column;
    align-items: stretch;
    padding: 0.75rem var(--container-pad) 1rem;
    gap: 0.25rem;
  }
  .nav-link { justify-content: flex-start; padding: 0.7rem 0.9rem; }
}

/* ---------- Footer ---------- */
.site-footer {
  background: linear-gradient(180deg, var(--c-surface-2), var(--c-bg));
  border-top: 1px solid var(--c-line);
  margin-top: 5rem;
  padding: 2.5rem 0 1.75rem;
}
.footer-inner {
  display: grid;
  grid-template-columns: 1.2fr 1fr 1fr;
  gap: 2rem;
  align-items: start;
}
.footer-brand { display: flex; gap: 0.85rem; align-items: center; }
.footer-logo { width: 38px; height: 38px; }
.footer-title { margin: 0; font-weight: 700; color: var(--c-ink); }
.footer-tag { margin: 0; font-size: 0.85rem; color: var(--c-muted); }
.footer-nav h2 { font-size: 0.9rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--c-muted); margin: 0 0 0.6rem; }
.footer-nav ul { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.35rem; }
.footer-nav a { color: var(--c-ink-soft); text-decoration: none; transition: color 160ms ease; }
.footer-nav a:hover { color: var(--c-primary); }
.footer-meta p { margin: 0 0 0.25rem; color: var(--c-ink-soft); font-size: 0.92rem; }
.footer-meta .muted { color: var(--c-muted); font-size: 0.85rem; }

@media (max-width: 760px) {
  .footer-inner { grid-template-columns: 1fr; gap: 1.4rem; }
}

/* ---------- Home page ---------- */
.hero {
  padding: 3.5rem 0 2rem;
  text-align: center;
}
.hero-logo-row { display: flex; justify-content: center; margin-bottom: 1.5rem; }
.hero-logo {
  width: clamp(120px, 18vw, 184px);
  height: clamp(120px, 18vw, 184px);
  filter: drop-shadow(0 18px 38px rgba(31, 60, 136, 0.18));
  transition: transform 320ms ease;
}
.hero-logo:hover { transform: translateY(-3px) scale(1.02); }
.hero-title {
  font-size: clamp(2rem, 4.4vw, 3.2rem);
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin: 0 0 0.75rem;
  background: linear-gradient(135deg, var(--c-primary-strong), var(--c-primary), var(--c-accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero-tagline {
  font-size: clamp(1rem, 1.7vw, 1.2rem);
  color: var(--c-muted);
  margin: 0 auto 1.25rem;
  max-width: 760px;
}
.hero-paragraphs {
  max-width: 880px;
  margin: 0 auto;
  font-size: 1.07rem;
  color: var(--c-ink-soft);
}
.hero-paragraphs p { margin: 0.85rem 0; }

.cta-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
  max-width: 980px;
  margin: 2rem auto 0;
}
.cta {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding: 1rem 1.15rem;
  border-radius: var(--radius);
  text-decoration: none;
  color: #fff;
  font-weight: 600;
  box-shadow: var(--shadow-1);
  transition: transform 180ms ease, box-shadow 180ms ease;
}
.cta:hover { transform: translateY(-2px); box-shadow: var(--shadow-2); }
.cta .cta-icon {
  width: 42px; height: 42px;
  display: grid; place-items: center;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.18);
  flex-shrink: 0;
}
.cta .cta-icon .icon { width: 24px; height: 24px; color: #fff; }
.cta-1 { background: linear-gradient(135deg, #3a7bd5, #1f3c88); }
.cta-2 { background: linear-gradient(135deg, #00b4a6, #008f86); }
.cta-3 { background: linear-gradient(135deg, #ef8354, #c95d2a); }

.section-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: 1.25rem;
  margin: 3rem 0 1rem;
}
.section-card {
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: 1.5rem 1.4rem;
  box-shadow: var(--shadow-1);
  transition: transform 220ms ease, box-shadow 220ms ease, border-color 220ms ease;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  text-decoration: none;
  color: inherit;
}
.section-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-2);
  border-color: var(--c-primary-tint);
}
.section-card .card-icon {
  width: 46px; height: 46px;
  display: grid; place-items: center;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--c-primary-tint), var(--c-accent-tint));
  color: var(--c-primary-strong);
}
.section-card .card-icon .icon { width: 26px; height: 26px; }
.section-card h2 {
  margin: 0;
  font-size: 1.18rem;
  color: var(--c-primary-strong);
  letter-spacing: -0.01em;
}
.section-card p { margin: 0; color: var(--c-ink-soft); font-size: 0.96rem; }
.section-card .card-cta {
  margin-top: auto;
  font-weight: 600;
  color: var(--c-primary);
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}
.section-card .card-cta .icon {
  width: 16px;
  height: 16px;
  transition: transform 200ms ease;
}
.section-card:hover .card-cta .icon { transform: translateX(3px); }
.section-card:hover .card-cta { color: var(--c-primary-strong); }

.home-intro h2 {
  text-align: center;
  font-size: clamp(1.4rem, 2.4vw, 1.8rem);
  margin: 2.5rem 0 0.5rem;
  color: var(--c-ink);
}
.home-intro p {
  text-align: center;
  max-width: 880px;
  margin: 0 auto;
  color: var(--c-ink-soft);
}

/* ---------- Page shell (content pages) ---------- */
/* Use padding-block so we don't reset the inherited padding-inline from .container. */
.page-shell { padding-block: 1rem 3rem; }

.breadcrumbs {
  margin: 1rem 0 1.25rem;
  font-size: 0.92rem;
  color: var(--c-muted);
}
.breadcrumbs ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.2rem 0.4rem;
  align-items: center;
}
.breadcrumbs a {
  color: var(--c-primary);
  text-decoration: none;
  border-bottom: 1px dashed transparent;
  transition: border-color 160ms ease, color 160ms ease;
}
.breadcrumbs a:hover { border-bottom-color: var(--c-primary); color: var(--c-primary-strong); }
.breadcrumbs .crumb-sep { color: var(--c-muted); margin: 0 0.15rem; }
.breadcrumbs [aria-current="page"] { color: var(--c-ink); font-weight: 600; }

/* ---------- Prose (content body) ---------- */
.prose {
  max-width: none;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius);
  padding: clamp(1.4rem, 3vw, 2.6rem) clamp(1.2rem, 3.5vw, 3rem);
  box-shadow: var(--shadow-1);
}

.prose > * + * { margin-top: 1.1em; }
.prose > h1 { margin-top: 0; }

.prose h1, .prose h2, .prose h3, .prose h4, .prose h5, .prose h6 {
  font-family: var(--ff-sans);
  line-height: 1.2;
  letter-spacing: -0.015em;
  color: var(--c-ink);
  scroll-margin-top: calc(var(--header-h) + 16px);
}
.prose h1 {
  font-size: clamp(1.85rem, 3.3vw, 2.6rem);
  background: linear-gradient(135deg, var(--c-primary-strong), var(--c-primary), var(--c-accent));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.prose h2 {
  font-size: clamp(1.4rem, 2.3vw, 1.7rem);
  padding-bottom: 0.35rem;
  border-bottom: 2px solid var(--c-line-soft);
  color: var(--c-primary-strong);
}
.prose h3 { font-size: 1.25rem; color: var(--c-ink); }
.prose h4 { font-size: 1.08rem; color: var(--c-ink-soft); }

.prose p { color: var(--c-ink); }
.prose a {
  color: var(--c-primary);
  text-decoration: none;
  background-image: linear-gradient(currentColor, currentColor);
  background-position: 0 100%;
  background-repeat: no-repeat;
  background-size: 100% 1px;
  transition: color 160ms ease, background-size 160ms ease;
  padding-bottom: 1px;
}
.prose a:hover {
  color: var(--c-primary-strong);
  background-size: 100% 2px;
}

.prose strong { color: var(--c-ink); font-weight: 700; }

.prose ul, .prose ol { padding-left: 1.4rem; }
.prose li + li { margin-top: 0.25rem; }

.prose blockquote {
  margin: 1.3em 0;
  padding: 0.85rem 1.15rem;
  border-left: 4px solid var(--c-primary);
  background: var(--c-primary-tint);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--c-ink-soft);
}

.prose hr {
  border: none;
  border-top: 1px solid var(--c-line);
  margin: 2.2em 0;
}

/* Header anchor link */
.prose .header-anchor {
  color: inherit;
  background: none;
  text-decoration: none;
}
.prose .header-anchor:hover { color: var(--c-primary); background: none; }

/* Inline code */
.prose :not(pre) > code {
  font-family: var(--ff-mono);
  background: var(--c-surface-2);
  color: var(--c-code-ink);
  font-size: 0.92em;
  padding: 0.12em 0.4em;
  border-radius: 5px;
  border: none;
  white-space: break-spaces;
}

/* Codeblocks (wrapped by markdown-it custom fence) */
.code-block {
  position: relative;
  margin: 1.4em 0;
  border-radius: var(--radius-sm);
  background: var(--c-code-bg);
  border: 1px solid var(--c-line-soft);
  overflow: hidden;
}
.code-block pre {
  margin: 0;
  padding: 1.05rem 1.1rem;
  overflow-x: auto;
  font-family: var(--ff-mono);
  font-size: 0.88rem;
  line-height: 1.55;
  color: var(--c-code-ink);
  background: transparent;
}
.code-block .code-lang {
  position: absolute;
  top: 0.55rem;
  left: 0.95rem;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--c-muted);
  font-family: var(--ff-mono);
  user-select: none;
}
.code-block:has(.code-lang) pre { padding-top: 1.75rem; }
.code-block .copy-btn {
  position: absolute;
  top: 0.45rem;
  right: 0.55rem;
  appearance: none;
  border: 1px solid var(--c-line);
  background: var(--c-surface);
  color: var(--c-ink-soft);
  font-size: 0.74rem;
  font-family: var(--ff-sans);
  font-weight: 600;
  padding: 0.28rem 0.6rem;
  border-radius: 6px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 160ms ease, transform 160ms ease, color 160ms ease, background 160ms ease;
}
.code-block:hover .copy-btn,
.code-block:focus-within .copy-btn { opacity: 1; }
.code-block .copy-btn:hover { color: var(--c-primary-strong); background: var(--c-primary-tint); }
.code-block .copy-btn.is-copied { color: var(--c-accent-strong); background: var(--c-accent-tint); border-color: var(--c-accent-tint); }

/* Tables */
.prose table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.4em 0;
  font-size: 0.95rem;
  display: block;
  overflow-x: auto;
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
}
.prose table thead { background: var(--c-surface-2); }
.prose table th,
.prose table td {
  padding: 0.7rem 0.9rem;
  text-align: left;
  border-bottom: 1px solid var(--c-line-soft);
}
.prose table th { color: var(--c-primary-strong); font-weight: 700; }
.prose table tbody tr:nth-child(even) { background: rgba(231, 239, 252, 0.35); }
.prose table tbody tr:last-child td { border-bottom: none; }

/* Task list (checkboxes) */
.prose .task-list-item,
.prose ul li.task-list-item {
  list-style: none;
  margin-left: -1.4em;
  padding-left: 0;
}
.prose .task-list-item input[type="checkbox"] {
  margin-right: 0.55em;
  width: 1.05em;
  height: 1.05em;
  vertical-align: -0.15em;
  accent-color: var(--c-primary);
  cursor: pointer;
}
.prose .task-list-item.is-checked,
.prose .task-list-item input[type="checkbox"]:checked + * {
  /* applied via JS on the li when input is checked */
}
.prose .task-list-item.is-checked {
  color: var(--c-muted);
  text-decoration: line-through;
}

/* FAQ / accordion: native <details> */
.prose details {
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
  background: var(--c-surface);
  padding: 0;
  margin: 0.8em 0;
  overflow: hidden;
  transition: box-shadow 200ms ease;
}
.prose details[open] { box-shadow: var(--shadow-1); }
.prose details > summary {
  list-style: none;
  cursor: pointer;
  padding: 0.85rem 1.1rem;
  font-weight: 600;
  color: var(--c-primary-strong);
  background: linear-gradient(180deg, var(--c-primary-tint), transparent);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}
.prose details > summary::-webkit-details-marker { display: none; }
.prose details > summary::after {
  content: "+";
  font-weight: 700;
  font-size: 1.2rem;
  color: var(--c-primary);
  transition: transform 200ms ease;
}
.prose details[open] > summary::after { content: "−"; }
.prose details > *:not(summary) { padding: 0 1.1rem; }
.prose details > *:nth-child(2) { padding-top: 0.6rem; }
.prose details > *:last-child:not(summary) { padding-bottom: 1rem; }

/* Mermaid */
.mermaid {
  background: var(--c-surface-2);
  border: 1px solid var(--c-line-soft);
  border-radius: var(--radius-sm);
  padding: 1rem;
  margin: 1.4em 0;
  text-align: center;
  overflow-x: auto;
}

/* KaTeX */
.katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.4em 0;
}

/* Related blocks */
.related {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--c-line);
}
.related h2 {
  font-size: 1.1rem;
  color: var(--c-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin: 0 0 1rem;
}
.related-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 0.6rem;
}
.related-list a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  padding: 0.75rem 0.95rem;
  background: var(--c-surface);
  border: 1px solid var(--c-line);
  border-radius: var(--radius-sm);
  color: var(--c-ink);
  text-decoration: none;
  font-weight: 500;
  transition: border-color 160ms ease, background 160ms ease, transform 160ms ease, color 160ms ease;
}
.related-list a:hover {
  border-color: var(--c-primary);
  background: var(--c-primary-tint);
  color: var(--c-primary-strong);
  transform: translateY(-1px);
}
.related-list .related-arrow { color: var(--c-primary); font-weight: 700; }

/* Focus rings */
:focus-visible {
  outline: 2px solid var(--c-primary);
  outline-offset: 2px;
  border-radius: 6px;
}

/* Print friendliness */
@media print {
  .site-header, .site-footer, .nav-toggle, .copy-btn, .breadcrumbs, .related { display: none; }
  .prose { box-shadow: none; border: none; padding: 0; }
}

/* Widescreen tuning */
@media (min-width: 1500px) {
  :root { --container-max: 1480px; }
  body { font-size: 17.5px; }
}