/* EngiRef landing site — palette derived from app icon:
   deep navy #0A1E5A → bright blue #1E4FD8 gradient, white sigma, amber #F5A800 rule */
:root {
  --bg: #f6f8fd;
  --surface: #ffffff;
  --surface-2: #eef2fb;
  --ink: #101828;
  --ink-soft: #3d4a63;
  --ink-faint: #5b6a86;
  --navy: #0a1e5a;
  --blue: #1e4fd8;
  --blue-deep: #16359c;
  --link: #1738b8;
  --amber: #f5a800;
  --amber-ink: #8a5b00;
  --line: #d7dff0;
  --hero-ink: #ffffff;
  --shadow: 0 10px 30px rgba(10, 30, 90, 0.10);
  --radius: 14px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a1026;
    --surface: #121a38;
    --surface-2: #182350;
    --ink: #e8edfa;
    --ink-soft: #b8c4e0;
    --ink-faint: #93a2c6;
    --navy: #0a1e5a;
    --blue: #6b8cff;
    --blue-deep: #9db2ff;
    --link: #9db2ff;
    --amber: #ffb62e;
    --amber-ink: #ffc85c;
    --line: #2b3a6e;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation: none !important; transition: none !important; }
}
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  font-size: 1.0625rem;
}
img { max-width: 100%; height: auto; }
a { color: var(--link); }
a:hover { text-decoration-thickness: 2px; }
:focus-visible {
  outline: 3px solid var(--amber);
  outline-offset: 2px;
  border-radius: 4px;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--navy);
  color: #fff;
  padding: 0.6rem 1rem;
  z-index: 100;
  border-radius: 0 0 8px 0;
}
.skip-link:focus { left: 0; }

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 1.25rem; }

/* Header / nav */
.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 50;
}
.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 64px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
  font-size: 1.1rem;
}
.brand img { border-radius: 9px; }
.brand .sigma { color: var(--blue); }
.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.45rem 0.7rem;
  font: inherit;
  color: var(--ink);
  cursor: pointer;
}
.site-nav ul {
  display: flex;
  gap: 1.4rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.site-nav a {
  color: var(--ink-soft);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.97rem;
}
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--link); }
@media (max-width: 720px) {
  .nav-toggle { display: block; }
  .site-nav { display: none; width: 100%; }
  .site-nav.open { display: block; }
  .site-header .wrap { flex-wrap: wrap; }
  .site-nav ul { flex-direction: column; gap: 0; padding: 0.5rem 0 1rem; }
  .site-nav a { display: block; padding: 0.6rem 0.25rem; }
}

/* Hero */
.hero {
  background: linear-gradient(135deg, #0a1e5a 0%, #16359c 55%, #1e4fd8 100%);
  color: var(--hero-ink);
  padding: 4rem 0 4.5rem;
  position: relative;
  overflow: hidden;
}
.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(315deg, rgba(255,255,255,0.06) 0 50%, transparent 50%);
  pointer-events: none;
}
.hero .wrap {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 3rem;
  align-items: center;
  position: relative;
  z-index: 1;
}
.hero h1 {
  font-size: clamp(1.9rem, 4.5vw, 2.9rem);
  line-height: 1.15;
  margin: 0 0 1rem;
  letter-spacing: -0.02em;
}
.hero h1 .accent {
  color: var(--amber);
  border-bottom: 4px solid var(--amber);
}
.hero .tagline {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  color: #d8e2ff;
  margin: 0 0 1.75rem;
  max-width: 34rem;
}
.hero .eyebrow {
  display: inline-block;
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.25);
  border-radius: 99px;
  padding: 0.3rem 0.9rem;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 1.2rem;
}
.store-buttons { display: flex; flex-wrap: wrap; gap: 0.8rem; align-items: center; }
.store-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  background: #000;
  color: #fff;
  border: 1px solid rgba(255,255,255,0.5);
  border-radius: 10px;
  padding: 0.55rem 1.1rem;
  text-decoration: none;
  line-height: 1.2;
}
.store-btn:hover { background: #111a30; }
.store-btn svg { flex: none; }
.store-btn .small { display: block; font-size: 0.68rem; opacity: 0.85; }
.store-btn .big { display: block; font-size: 1.05rem; font-weight: 700; }
.hero-note { margin-top: 1rem; font-size: 0.9rem; color: #b9c8f5; }

/* Hero mock panel (text mock — no screenshots published for this app) */
.mock-card {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.22);
  border-radius: var(--radius);
  padding: 1.5rem;
  backdrop-filter: blur(4px);
  box-shadow: var(--shadow);
}
.mock-card .icon-row {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  margin-bottom: 1.2rem;
}
.mock-card .icon-row img { border-radius: 14px; box-shadow: 0 4px 14px rgba(0,0,0,0.35); }
.mock-card .icon-row strong { font-size: 1.15rem; }
.mock-card .icon-row span { display: block; font-size: 0.85rem; color: #c4d1f8; }
.stat-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin: 0;
}
.stat-grid > div {
  background: rgba(10, 30, 90, 0.55);
  border: 1px solid rgba(255,255,255,0.14);
  border-radius: 10px;
  padding: 0.8rem 0.9rem;
}
.stat-grid dt { font-size: 1.35rem; font-weight: 800; color: var(--amber); }
.stat-grid dd { margin: 0; font-size: 0.85rem; color: #d8e2ff; }
@media (max-width: 860px) {
  .hero .wrap { grid-template-columns: 1fr; }
  .mock-card { max-width: 440px; }
}

/* Sections */
section { padding: 3.5rem 0; }
section.alt { background: var(--surface); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
h2 {
  font-size: clamp(1.5rem, 3vw, 2.05rem);
  line-height: 1.2;
  margin: 0 0 0.6rem;
  letter-spacing: -0.01em;
}
.kicker {
  color: var(--amber-ink);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.82rem;
  margin: 0 0 0.4rem;
}
.lede { color: var(--ink-soft); max-width: 46rem; margin: 0 0 2rem; font-size: 1.1rem; }

/* Problem / solution */
.split { display: grid; grid-template-columns: 1fr 1fr; gap: 2rem; }
.panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.6rem 1.7rem;
}
section.alt .panel { background: var(--surface-2); }
.panel h3 { margin: 0 0 0.7rem; font-size: 1.2rem; }
.panel ul { margin: 0; padding-left: 1.2rem; color: var(--ink-soft); }
.panel li { margin: 0.45rem 0; }
.panel.solution { border-top: 4px solid var(--amber); }
.panel.problem { border-top: 4px solid var(--blue); }
@media (max-width: 720px) { .split { grid-template-columns: 1fr; } }

/* Features grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
  gap: 1.25rem;
}
.feature {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.4rem 1.5rem;
}
section.alt .feature { background: var(--surface-2); }
.feature h3 {
  margin: 0 0 0.5rem;
  font-size: 1.08rem;
  display: flex;
  align-items: center;
  gap: 0.55rem;
}
.feature .glyph {
  flex: none;
  width: 34px;
  height: 34px;
  border-radius: 9px;
  background: linear-gradient(135deg, var(--navy), #1e4fd8);
  color: #fff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 1rem;
}
.feature p { margin: 0; color: var(--ink-soft); font-size: 0.98rem; }

/* Audience cards */
.audience-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1.25rem; }
.audience {
  border-left: 4px solid var(--amber);
  background: var(--surface);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 1.3rem 1.5rem;
  border-top: 1px solid var(--line);
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.audience h3 { margin: 0 0 0.4rem; font-size: 1.05rem; color: var(--blue-deep); }
.audience p { margin: 0; color: var(--ink-soft); font-size: 0.98rem; }

/* FAQ accordion */
.faq-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  margin-bottom: 0.75rem;
  overflow: hidden;
}
.faq-item h3 { margin: 0; font-size: 1rem; }
.faq-item button {
  width: 100%;
  text-align: left;
  background: none;
  border: 0;
  font: inherit;
  font-weight: 650;
  color: var(--ink);
  padding: 1rem 3rem 1rem 1.2rem;
  cursor: pointer;
  position: relative;
}
.faq-item button::after {
  content: "+";
  position: absolute;
  right: 1.1rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.4rem;
  color: var(--amber-ink);
  font-weight: 400;
}
.faq-item button[aria-expanded="true"]::after { content: "\2212"; }
.faq-item .faq-answer { padding: 0 1.2rem 1.1rem; color: var(--ink-soft); }
.faq-item .faq-answer[hidden] { display: none; }
.faq-item .faq-answer p { margin: 0; }

/* Guides listing */
.guide-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.25rem; }
.guide-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.4rem 1.5rem;
  text-decoration: none;
  color: var(--ink);
  transition: border-color 0.15s ease, transform 0.15s ease;
}
.guide-card:hover { border-color: var(--blue); transform: translateY(-2px); }
.guide-card h3 { margin: 0 0 0.45rem; font-size: 1.08rem; color: var(--link); }
.guide-card p { margin: 0; color: var(--ink-soft); font-size: 0.95rem; }
.guide-card .more { display: inline-block; margin-top: 0.7rem; font-weight: 650; color: var(--amber-ink); font-size: 0.9rem; }

/* CTA band */
.cta-band {
  background: linear-gradient(135deg, #0a1e5a, #1e4fd8);
  color: #fff;
  text-align: center;
  padding: 3.5rem 0;
}
.cta-band h2 { color: #fff; }
.cta-band p { color: #d8e2ff; max-width: 40rem; margin: 0.5rem auto 1.6rem; }
.cta-band .store-buttons { justify-content: center; }

/* Footer */
.site-footer {
  background: var(--surface);
  border-top: 1px solid var(--line);
  padding: 2.5rem 0 2rem;
  color: var(--ink-faint);
  font-size: 0.95rem;
}
.site-footer .cols {
  display: grid;
  grid-template-columns: 1.2fr 1fr 1fr;
  gap: 2rem;
  margin-bottom: 1.5rem;
}
.site-footer h3 { font-size: 0.95rem; margin: 0 0 0.6rem; color: var(--ink); }
.site-footer ul { list-style: none; margin: 0; padding: 0; }
.site-footer li { margin: 0.35rem 0; }
.site-footer .fine { border-top: 1px solid var(--line); padding-top: 1.2rem; font-size: 0.85rem; }
@media (max-width: 720px) { .site-footer .cols { grid-template-columns: 1fr; } }

/* Article pages */
.breadcrumb { font-size: 0.9rem; color: var(--ink-faint); margin: 1.5rem 0 0; }
.breadcrumb ol { list-style: none; display: flex; flex-wrap: wrap; gap: 0.4rem; margin: 0; padding: 0; }
.breadcrumb li + li::before { content: "/"; margin-right: 0.4rem; color: var(--line); }
article.guide { max-width: 46rem; margin: 0 auto; padding: 1.5rem 0 3.5rem; }
article.guide h1 { font-size: clamp(1.7rem, 4vw, 2.4rem); line-height: 1.18; letter-spacing: -0.015em; margin: 0.8rem 0 0.5rem; }
article.guide .byline { color: var(--ink-faint); font-size: 0.9rem; margin-bottom: 1.8rem; }
article.guide h2 { font-size: 1.45rem; margin-top: 2.4rem; }
article.guide h3 { font-size: 1.15rem; margin-top: 1.8rem; }
article.guide p, article.guide li { color: var(--ink-soft); }
article.guide table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  margin: 1.2rem 0;
}
article.guide .table-scroll { overflow-x: auto; }
article.guide th, article.guide td {
  border: 1px solid var(--line);
  padding: 0.55rem 0.75rem;
  text-align: left;
}
article.guide th { background: var(--surface-2); color: var(--ink); }
article.guide code, article.guide .formula {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 0.1rem 0.4rem;
  font-size: 0.92em;
  color: var(--ink);
}
article.guide .formula-block {
  display: block;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-left: 4px solid var(--amber);
  border-radius: 8px;
  padding: 0.9rem 1.1rem;
  margin: 1.2rem 0;
  overflow-x: auto;
  color: var(--ink);
}
.app-tie-in {
  background: var(--surface);
  border: 1px solid var(--line);
  border-left: 5px solid var(--blue);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 1.3rem 1.5rem;
  margin: 2.4rem 0 0;
}
.app-tie-in h2 { margin-top: 0 !important; }
.related-guides { margin-top: 2.5rem; padding-top: 1.5rem; border-top: 1px solid var(--line); }
.related-guides h2 { font-size: 1.15rem; margin: 0 0 0.7rem; }
.related-guides ul { padding-left: 1.2rem; margin: 0; }
.related-guides li { margin: 0.4rem 0; }