/* ==========================================================================
   Telecom Network Fault Correlation & Ticket Routing Automation
   Light, elegant, professional theme. Mobile → desktop → widescreen.
   ========================================================================== */

/* ----------------------------------------------------------------- tokens */
:root {
  /* Brand palette */
  --brand: #0d7490;
  --brand-strong: #155e75;
  --brand-soft: #e0f2f7;
  --accent: #4f46e5;
  --accent-soft: #eceafe;
  --signal: #f59e0b;
  --signal-soft: #fef3e2;
  --success: #059669;
  --critical: #e11d48;

  /* Surfaces & ink */
  --bg: #f6f8fb;
  --bg-tint: #eef3f8;
  --surface: #ffffff;
  --surface-2: #f4f7fa;
  --ink: #16202e;
  --ink-soft: #33425a;
  --muted: #5b6b82;
  --line: #e2e8f0;
  --line-strong: #cbd5e1;

  /* Code */
  --code-bg: #f4f7fa;
  --code-inline-bg: #eef2f7;
  --code-border: #e3e9f1;

  /* Gradients */
  --grad-brand: linear-gradient(135deg, #06b6d4 0%, #0e7490 52%, #4f46e5 100%);

  /* Geometry */
  --header-height: 66px;
  --container: 1240px;
  --container-wide: 1400px;
  --radius: 14px;
  --radius-sm: 9px;
  --radius-lg: 22px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(16, 32, 46, 0.06), 0 1px 3px rgba(16, 32, 46, 0.05);
  --shadow: 0 6px 18px rgba(16, 32, 46, 0.08);
  --shadow-lg: 0 18px 44px rgba(16, 32, 46, 0.14);

  /* Type */
  --font-sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", ui-monospace, "Cascadia Code", Menlo, Consolas, monospace;

  --transition: 160ms ease;
}

/* ------------------------------------------------------------------ reset */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 1.02rem;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

.icon {
  width: 1.25em;
  height: 1.25em;
  flex: none;
  vertical-align: -0.18em;
}
.icon-sm { width: 1em; height: 1em; }
.icon-xs { width: 0.85em; height: 0.85em; }

/* --------------------------------------------------------------- layout */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: clamp(1rem, 4vw, 2.5rem);
}

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

.content-shell {
  padding-block: clamp(1.4rem, 3vw, 2.6rem) clamp(2.5rem, 5vw, 4rem);
}

/* --------------------------------------------------------- skip link */
.skip-link {
  position: absolute;
  left: 0.75rem;
  top: -3rem;
  z-index: 200;
  background: var(--brand);
  color: #fff;
  padding: 0.55rem 0.95rem;
  border-radius: var(--radius-sm);
  transition: top var(--transition);
}
.skip-link:focus {
  top: 0.75rem;
}

/* ------------------------------------------------------------- headings */
h1, h2, h3, h4 {
  line-height: 1.22;
  color: var(--ink);
  font-weight: 700;
  letter-spacing: -0.012em;
  scroll-margin-top: calc(var(--header-height) + 1rem);
}

p { margin: 0 0 1.1rem; }

/* ----------------------------------------------------------------- links */
a {
  color: var(--brand);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: var(--accent); }

.prose a {
  color: var(--brand-strong);
  text-decoration: underline;
  text-decoration-color: color-mix(in srgb, var(--brand) 35%, transparent);
  text-underline-offset: 0.18em;
  text-decoration-thickness: 1.5px;
  transition: color var(--transition), text-decoration-color var(--transition), background var(--transition);
  border-radius: 3px;
}
.prose a:hover {
  color: var(--accent);
  text-decoration-color: var(--accent);
  background: color-mix(in srgb, var(--accent-soft) 70%, transparent);
}

:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--accent) 55%, transparent);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ============================================================ HEADER */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  backdrop-filter: saturate(150%) blur(10px);
  border-bottom: 1px solid var(--line);
}
.header-inner {
  display: flex;
  align-items: center;
  gap: 1rem;
  min-height: var(--header-height);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  color: var(--ink);
  font-weight: 700;
}
.brand-logo { width: 40px; height: 40px; transition: transform var(--transition); }
.brand:hover .brand-logo { transform: rotate(-6deg) scale(1.05); }
.brand-text { display: flex; flex-direction: column; line-height: 1.1; }
.brand-name { font-size: 1.02rem; letter-spacing: -0.02em; }
.brand-sub { font-size: 0.72rem; font-weight: 500; color: var(--muted); letter-spacing: 0.01em; }

.primary-nav { margin-left: auto; }
.nav-list {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.5rem 0.8rem;
  border-radius: var(--radius-sm);
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 0.93rem;
  position: relative;
  transition: color var(--transition), background var(--transition);
}
.nav-link .icon { color: var(--brand); transition: color var(--transition); }
.nav-link:hover {
  color: var(--brand-strong);
  background: var(--brand-soft);
}
.nav-link.is-current {
  color: var(--brand-strong);
  background: var(--brand-soft);
}
.nav-link.is-current::after {
  content: "";
  position: absolute;
  left: 0.8rem;
  right: 0.8rem;
  bottom: -1px;
  height: 2px;
  border-radius: 2px;
  background: var(--grad-brand);
}

.nav-toggle {
  display: none;
  margin-left: auto;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition);
}
.nav-toggle:hover { background: var(--brand-soft); border-color: var(--brand); }
.nav-toggle .icon-close { display: none; }
.nav-toggle[aria-expanded="true"] .icon-menu { display: none; }
.nav-toggle[aria-expanded="true"] .icon-close { display: block; }

/* ============================================================== FOOTER */
.site-footer {
  flex-shrink: 0;
  margin-top: auto;
  background: #0f2434;
  color: #cdd9e6;
  border-top: 3px solid transparent;
  border-image: var(--grad-brand) 1;
}
.footer-inner {
  display: flex;
  flex-wrap: wrap;
  gap: 2.5rem;
  justify-content: space-between;
  padding-block: 2.4rem 1.6rem;
}
.footer-brand { display: flex; gap: 0.85rem; align-items: flex-start; max-width: 26rem; }
.footer-logo { width: 36px; height: 36px; }
.footer-name { margin: 0; font-weight: 700; color: #fff; font-size: 1.05rem; }
.footer-tagline { margin: 0.25rem 0 0; color: #9fb3c6; font-size: 0.9rem; }
.footer-heading {
  margin: 0 0 0.7rem;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: #7f97ac;
}
.footer-nav ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.35rem; }
.footer-nav a {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: #cdd9e6;
  font-weight: 500;
  padding: 0.2rem 0;
}
.footer-nav a .icon { color: #4cc2dc; }
.footer-nav a:hover { color: #fff; }
.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-block: 1.1rem 1.4rem;
}
.footer-bottom p { margin: 0; font-size: 0.84rem; color: #8fa3b6; }

/* =============================================================== HERO */
.hero {
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(80rem 40rem at 85% -25%, rgba(79, 70, 229, 0.10), transparent 60%),
    radial-gradient(60rem 32rem at 5% 0%, rgba(6, 182, 212, 0.12), transparent 55%),
    var(--bg);
  border-bottom: 1px solid var(--line);
}
.hero-inner {
  padding-block: clamp(2.6rem, 6vw, 5rem) clamp(2.4rem, 5vw, 4.2rem);
  text-align: center;
}
.hero-logo-row { display: flex; justify-content: center; margin-bottom: 1.4rem; }
.hero-logo {
  width: clamp(96px, 14vw, 136px);
  height: auto;
  filter: drop-shadow(0 12px 26px rgba(13, 116, 144, 0.32));
  transition: transform var(--transition);
}
.hero-logo:hover { transform: translateY(-4px) scale(1.03); }

.hero-title {
  margin: 0 auto 1.1rem;
  font-size: clamp(1.9rem, 4.6vw, 3.25rem);
  letter-spacing: -0.025em;
  max-width: 20ch;
}
.hero-title-accent {
  background: var(--grad-brand);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero-lead {
  font-size: clamp(1.08rem, 1.9vw, 1.4rem);
  font-weight: 500;
  color: var(--ink-soft);
  max-width: 60ch;
  margin: 0 auto 1.2rem;
}
.hero-text {
  color: var(--muted);
  max-width: 74ch;
  margin: 0 auto 1rem;
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  justify-content: center;
  margin-top: 1.9rem;
}
.cta {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.8rem 1.25rem;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
  color: var(--ink);
  font-weight: 650;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.cta:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow);
  color: var(--ink);
}
.cta-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.1rem;
  height: 2.1rem;
  border-radius: 10px;
  color: #fff;
}
.cta-arrow { color: var(--muted); transition: transform var(--transition); margin-left: 0.1rem; }
.cta:hover .cta-arrow { transform: translateX(4px); }
.cta-1 .cta-icon { background: linear-gradient(135deg, #0891b2, #0e7490); }
.cta-1:hover { border-color: #0891b2; }
.cta-2 .cta-icon { background: linear-gradient(135deg, #f59e0b, #d97706); }
.cta-2:hover { border-color: #f59e0b; }
.cta-3 .cta-icon { background: linear-gradient(135deg, #6366f1, #4f46e5); }
.cta-3:hover { border-color: #6366f1; }

/* ===================================================== PIPELINE BAND */
.pipeline-band { padding-block: clamp(2rem, 4vw, 3.2rem) 0; }
.pipeline {
  list-style: none;
  margin: 1.6rem 0 0;
  padding: 0;
  display: flex;
  align-items: stretch;
  gap: 0.5rem;
}
.pipeline-stage {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 0.55rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.4rem 1rem;
  box-shadow: var(--shadow-sm);
  position: relative;
  overflow: hidden;
  transition: transform var(--transition), box-shadow var(--transition);
}
.pipeline-stage::before { content: ""; position: absolute; inset: 0 0 auto 0; height: 4px; }
.pipeline-stage:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.pipeline-icon {
  width: 3rem; height: 3rem;
  border-radius: 14px;
  display: grid; place-content: center;
  color: #fff;
}
.pipeline-icon .icon { width: 1.5rem; height: 1.5rem; }
.stage-1 .pipeline-icon { background: linear-gradient(135deg, #06b6d4, #0891b2); }
.stage-1::before { background: linear-gradient(90deg, #06b6d4, #0891b2); }
.stage-2 .pipeline-icon { background: linear-gradient(135deg, #f59e0b, #d97706); }
.stage-2::before { background: linear-gradient(90deg, #f59e0b, #d97706); }
.stage-3 .pipeline-icon { background: linear-gradient(135deg, #6366f1, #4f46e5); }
.stage-3::before { background: linear-gradient(90deg, #6366f1, #4f46e5); }
.stage-4 .pipeline-icon { background: linear-gradient(135deg, #10b981, #059669); }
.stage-4::before { background: linear-gradient(90deg, #10b981, #059669); }
.pipeline-name { font-weight: 700; color: var(--ink); }
.pipeline-desc { font-size: 0.85rem; color: var(--muted); line-height: 1.45; }
.pipeline-arrow { display: flex; align-items: center; justify-content: center; color: var(--brand); flex: none; }
.pipeline-arrow .icon { width: 1.6rem; height: 1.6rem; }

@media (max-width: 820px) {
  .pipeline { flex-direction: column; align-items: stretch; }
  .pipeline-arrow { transform: rotate(90deg); padding: 0.1rem 0; }
}

/* ===================================================== HOME SECTIONS */
.home-sections { padding-block: clamp(2.4rem, 5vw, 4rem); }
.section-title {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: clamp(1.4rem, 2.6vw, 1.9rem);
  margin: 0 0 0.5rem;
}
.section-title .icon { color: var(--brand); }
.section-intro { color: var(--muted); max-width: 70ch; margin: 0 0 2rem; }

.pillar-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 20rem), 1fr));
  gap: 1.4rem;
}
.pillar-card {
  display: flex;
  flex-direction: column;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.6rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
  position: relative;
  overflow: hidden;
}
.pillar-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: var(--grad-brand);
  opacity: 0.9;
}
.pillar-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: color-mix(in srgb, var(--brand) 40%, var(--line));
}
.pillar-head { display: flex; align-items: center; gap: 0.8rem; margin-bottom: 0.8rem; color: var(--ink); }
.pillar-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.7rem;
  height: 2.7rem;
  border-radius: 12px;
  color: #fff;
  flex: none;
}
.pillar-1 .pillar-icon { background: linear-gradient(135deg, #0891b2, #0e7490); }
.pillar-2 .pillar-icon { background: linear-gradient(135deg, #f59e0b, #d97706); }
.pillar-3 .pillar-icon { background: linear-gradient(135deg, #6366f1, #4f46e5); }
.pillar-name { margin: 0; font-size: 1.12rem; line-height: 1.25; }
.pillar-head:hover .pillar-name { color: var(--brand-strong); }
.pillar-blurb { color: var(--muted); font-size: 0.95rem; margin: 0 0 1rem; }
.pillar-links { list-style: none; margin: 0 0 1.2rem; padding: 0; display: grid; gap: 0.1rem; }
.pillar-links a {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.35rem 0.4rem;
  border-radius: var(--radius-sm);
  color: var(--ink-soft);
  font-size: 0.93rem;
  font-weight: 550;
}
.pillar-links a .icon { color: var(--brand); }
.pillar-links a:hover { background: var(--surface-2); color: var(--brand-strong); }
.pillar-cta {
  margin-top: auto;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-weight: 650;
  color: var(--brand-strong);
}
.pillar-cta .icon { transition: transform var(--transition); }
.pillar-cta:hover .icon { transform: translateX(4px); }

/* ========================================================= BREADCRUMBS */
.breadcrumbs ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.15rem;
  margin: 0 0 1.4rem;
  padding: 0;
  font-size: 0.86rem;
  color: var(--muted);
}
.breadcrumbs li { display: inline-flex; align-items: center; gap: 0.15rem; }
.breadcrumbs a { color: var(--muted); font-weight: 550; padding: 0.15rem 0.25rem; border-radius: 5px; }
.breadcrumbs a:hover { color: var(--brand-strong); background: var(--brand-soft); }
.breadcrumbs [aria-current="page"] { color: var(--ink-soft); font-weight: 650; }
.crumb-sep { color: var(--line-strong); display: inline-flex; }

/* ============================================================= ARTICLE */
.article {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  padding: clamp(1.4rem, 3.5vw, 3rem);
  box-shadow: var(--shadow-sm);
}

.prose > :first-child { margin-top: 0; }

.prose h1 {
  font-size: clamp(1.8rem, 3.6vw, 2.6rem);
  margin: 0 0 1.2rem;
  letter-spacing: -0.025em;
  background: var(--grad-brand);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  width: fit-content;
  max-width: 100%;
}
.prose h2 {
  font-size: clamp(1.4rem, 2.5vw, 1.85rem);
  margin: 2.4rem 0 1rem;
  padding-bottom: 0.45rem;
  border-bottom: 1px solid var(--line);
}
.prose h3 {
  font-size: clamp(1.18rem, 2vw, 1.4rem);
  margin: 1.9rem 0 0.8rem;
  color: var(--brand-strong);
}
.prose h4 { font-size: 1.1rem; margin: 1.5rem 0 0.6rem; color: var(--ink-soft); }

.prose p,
.prose li { color: var(--ink-soft); }
.prose strong { color: var(--ink); font-weight: 700; }

.prose ul,
.prose ol { margin: 0 0 1.2rem; padding-left: 1.4rem; }
.prose li { margin-bottom: 0.4rem; }
.prose li::marker { color: var(--brand); }

.prose blockquote {
  margin: 1.4rem 0;
  padding: 0.6rem 1.2rem;
  border-left: 4px solid var(--brand);
  background: var(--brand-soft);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--ink-soft);
}
.prose hr { border: none; border-top: 1px solid var(--line); margin: 2rem 0; }

/* Heading anchors */
.heading-anchor {
  color: var(--line-strong);
  margin-left: 0.4rem;
  font-weight: 500;
  opacity: 0;
  text-decoration: none;
  transition: opacity var(--transition), color var(--transition);
}
.prose h2:hover .heading-anchor,
.prose h3:hover .heading-anchor,
.prose h4:hover .heading-anchor { opacity: 1; }
.heading-anchor:hover { color: var(--accent); }

/* ------------------------------------------------------- inline code */
.prose :not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--code-inline-bg);
  color: var(--brand-strong);
  padding: 0.12em 0.4em;
  border-radius: 5px;
  word-break: break-word;
}

/* --------------------------------------------------------- code blocks */
.code-wrap {
  position: relative;
  margin: 1.5rem 0;
}
.prose pre[class*="language-"],
.prose pre {
  margin: 1.5rem 0;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  padding: 1.1rem 1.2rem;
  overflow-x: auto;
  font-size: 0.875rem;
  line-height: 1.6;
  tab-size: 4;
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.4);
}
.code-wrap pre { margin: 0; }
.prose pre code {
  font-family: var(--font-mono);
  background: none;
  padding: 0;
  color: #243244;
  font-size: inherit;
}

.copy-btn {
  position: absolute;
  top: 0.6rem;
  right: 0.6rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.35rem 0.6rem;
  font-size: 0.78rem;
  font-weight: 650;
  font-family: var(--font-sans);
  color: var(--ink-soft);
  background: var(--surface);
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  cursor: pointer;
  opacity: 0;
  transform: translateY(-3px);
  transition: opacity var(--transition), transform var(--transition), background var(--transition), color var(--transition);
}
.code-wrap:hover .copy-btn,
.copy-btn:focus-visible { opacity: 1; transform: translateY(0); }
.copy-btn:hover { background: var(--brand-soft); color: var(--brand-strong); border-color: var(--brand); }
.copy-btn.is-copied { background: var(--success); color: #fff; border-color: var(--success); opacity: 1; }
.copy-btn .icon { width: 0.95em; height: 0.95em; }
@media (hover: none) {
  .copy-btn { opacity: 1; transform: none; }
}

/* Prism light syntax theme (matches palette) */
.token.comment, .token.prolog, .token.cdata { color: #708096; font-style: italic; }
.token.punctuation { color: #64748b; }
.token.namespace { opacity: 0.7; }
.token.keyword, .token.boolean, .token.atrule, .token.rule { color: #4338ca; }
.token.operator { color: #475569; }
.token.string, .token.char, .token.attr-value, .token.inserted { color: #047857; }
.token.number, .token.constant, .token.symbol { color: #b45309; }
.token.function, .token.deleted { color: #0369a1; }
.token.class-name, .token.maybe-class-name, .token.builtin { color: #0e7490; }
.token.property, .token.tag, .token.attr-name { color: #0e7490; }
.token.decorator, .token.annotation { color: #b45309; }
.token.regex, .token.variable { color: #be185d; }
.token.important, .token.bold { font-weight: 700; }
.token.italic { font-style: italic; }

/* ------------------------------------------------------------- tables */
.table-scroll {
  overflow-x: auto;
  margin: 1.5rem 0;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  -webkit-overflow-scrolling: touch;
}
.table-scroll table {
  border-collapse: collapse;
  width: 100%;
  min-width: 36rem;
  font-size: 0.92rem;
}
.table-scroll th,
.table-scroll td {
  padding: 0.7rem 0.95rem;
  text-align: left;
  border-bottom: 1px solid var(--line);
  vertical-align: top;
}
.table-scroll thead th {
  background: var(--brand-soft);
  color: var(--brand-strong);
  font-weight: 700;
  white-space: nowrap;
  border-bottom: 2px solid color-mix(in srgb, var(--brand) 30%, var(--line));
}
.table-scroll tbody tr { transition: background var(--transition); }
.table-scroll tbody tr:nth-child(even) { background: var(--surface-2); }
.table-scroll tbody tr:hover { background: var(--brand-soft); }
.table-scroll tbody tr:last-child td { border-bottom: none; }

/* -------------------------------------------------- task list checkboxes */
.contains-task-list {
  list-style: none;
  padding-left: 0.25rem;
  margin: 1.2rem 0;
}
.contains-task-list .contains-task-list { margin: 0.4rem 0 0.4rem 1.4rem; }
.task-list-item {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  padding: 0.4rem 0.55rem;
  border-radius: var(--radius-sm);
  margin-bottom: 0.2rem;
  transition: background var(--transition);
}
.task-list-item::marker { content: ""; }
.task-list-item:hover { background: var(--surface-2); }
.task-list-item-checkbox {
  appearance: none;
  -webkit-appearance: none;
  margin: 0.28em 0 0;
  width: 1.2rem;
  height: 1.2rem;
  flex: none;
  border: 2px solid var(--line-strong);
  border-radius: 6px;
  background: var(--surface);
  cursor: pointer;
  display: grid;
  place-content: center;
  transition: background var(--transition), border-color var(--transition);
}
.task-list-item-checkbox::before {
  content: "";
  width: 0.7rem;
  height: 0.7rem;
  transform: scale(0);
  transition: transform var(--transition);
  background: #fff;
  clip-path: polygon(14% 47%, 0 60%, 40% 100%, 100% 22%, 86% 8%, 38% 70%);
}
.task-list-item-checkbox:checked {
  background: var(--brand);
  border-color: var(--brand);
}
.task-list-item-checkbox:checked::before { transform: scale(1); }
.task-list-item-checkbox:hover { border-color: var(--brand); }
.task-list-item-label { cursor: pointer; color: var(--ink-soft); transition: color var(--transition); }
.task-list-item-checkbox:checked + .task-list-item-label {
  text-decoration: line-through;
  text-decoration-color: var(--muted);
  color: var(--muted);
}

/* --------------------------------------------------------- accordions */
.prose details {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  margin: 0.8rem 0;
  background: var(--surface);
  overflow: hidden;
  transition: box-shadow var(--transition), border-color var(--transition);
}
.prose details[open] { box-shadow: var(--shadow-sm); border-color: var(--line-strong); }
.prose summary {
  cursor: pointer;
  padding: 0.9rem 1.1rem;
  font-weight: 650;
  color: var(--ink);
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  transition: background var(--transition);
}
.prose summary::-webkit-details-marker { display: none; }
.prose summary:hover { background: var(--brand-soft); color: var(--brand-strong); }
.prose summary::after {
  content: "";
  width: 0.6rem;
  height: 0.6rem;
  border-right: 2px solid var(--brand);
  border-bottom: 2px solid var(--brand);
  transform: rotate(45deg);
  transition: transform var(--transition);
  flex: none;
}
.prose details[open] summary::after { transform: rotate(225deg); }
.prose details > :not(summary) { padding-inline: 1.1rem; }
.prose details > p:last-child { padding-bottom: 1rem; }

/* ===================================================== RELATED / CARDS */
.related { margin-top: 2.6rem; }
.related-title {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  font-size: 1.25rem;
  margin: 0 0 1.1rem;
}
.related-title .icon { color: var(--brand); }

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 17rem), 1fr));
  gap: 1rem;
}
.card {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
  padding: 1.1rem 1.2rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  color: var(--ink);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow);
  border-color: color-mix(in srgb, var(--brand) 35%, var(--line));
  color: var(--ink);
}
.card-title { font-weight: 700; color: var(--brand-strong); line-height: 1.3; }
.card-desc { font-size: 0.88rem; color: var(--muted); line-height: 1.55; }
.card-cta {
  margin-top: auto;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.85rem;
  font-weight: 650;
  color: var(--brand);
}
.card .card-cta .icon { transition: transform var(--transition); }
.card:hover .card-cta .icon { transform: translateX(4px); }

.pill-list { list-style: none; display: flex; flex-wrap: wrap; gap: 0.6rem; margin: 0; padding: 0; }
.pill {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--line);
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 0.9rem;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition), border-color var(--transition), color var(--transition), background var(--transition);
}
.pill .icon { color: var(--brand); transition: transform var(--transition); }
.pill:hover {
  transform: translateY(-2px);
  border-color: var(--brand);
  color: var(--brand-strong);
  background: var(--brand-soft);
}
.pill:hover .icon { transform: translateX(3px); }

/* ----------------------------------------------------------- buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.7rem 1.2rem;
  border-radius: var(--radius);
  font-weight: 650;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform var(--transition), box-shadow var(--transition), background var(--transition);
}
.btn-primary {
  background: var(--grad-brand);
  color: #fff;
  box-shadow: var(--shadow-sm);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow); color: #fff; }

/* ----------------------------------------------------------- KaTeX */
.katex { font-size: 1.04em; }
.katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 0.6rem 0.2rem;
  margin: 1.4rem 0;
}
.prose .katex-display > .katex { color: var(--ink); }
.eq, .math.inline { color: var(--ink); }

/* ----------------------------------------------------------- mermaid */
.mermaid {
  margin: 1.6rem 0;
  text-align: center;
  background:
    radial-gradient(60rem 20rem at 50% -40%, rgba(13, 116, 144, 0.05), transparent 70%),
    var(--surface-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.4rem 1.2rem;
  overflow-x: auto;
  box-shadow: var(--shadow-sm);
}
.mermaid svg { max-width: 100%; height: auto; }
/* Fallback if rendering fails: show the source legibly instead of a blank box */
.mermaid-error {
  text-align: left;
  white-space: pre-wrap;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.5;
  color: var(--muted);
}
/* Optional caption rendered above a diagram via a bold lead-in paragraph */
.diagram-caption {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  font-weight: 650;
  color: var(--brand-strong);
  margin: 1.6rem 0 -0.6rem;
}
.diagram-caption .icon { color: var(--brand); }

/* offline card */
.offline-card { text-align: center; }
.offline-card .btn { margin-top: 0.6rem; }

/* ========================================================= RESPONSIVE */
@media (min-width: 1500px) {
  .container { max-width: var(--container-wide); }
}

@media (max-width: 820px) {
  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: fixed;
    inset: var(--header-height) 0 auto 0;
    background: var(--surface);
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-lg);
    margin-left: 0;
    max-height: 0;
    overflow: hidden;
    transition: max-height 220ms ease;
  }
  .primary-nav.is-open { max-height: 22rem; }
  .nav-list {
    flex-direction: column;
    align-items: stretch;
    gap: 0.15rem;
    padding: 0.8rem clamp(1rem, 4vw, 2.5rem) 1.1rem;
  }
  .nav-link { padding: 0.8rem 0.9rem; font-size: 1rem; }
  .nav-link.is-current::after { display: none; }
  .nav-link.is-current { box-shadow: inset 3px 0 0 var(--brand); }
}

@media (max-width: 560px) {
  body { font-size: 0.99rem; }
  .brand-sub { display: none; }
  .hero-cta { flex-direction: column; align-items: stretch; }
  .cta { justify-content: flex-start; }
  .article { border-radius: var(--radius); }
}

/* --------------------------------------------------- motion / a11y */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}