/* PhysRef landing site — palette derived from app icon:
   orange integral (#F26A1B) on near-black (#131419) */

:root {
  --accent: #e05e12;
  --accent-strong: #c85009;
  --accent-soft: #fdeadd;
  --ink: #1c1d24;
  --ink-soft: #4b4d59;
  --bg: #faf8f5;
  --surface: #ffffff;
  --surface-alt: #f3efe9;
  --line: #e4ded4;
  --dark-panel: #131419;
  --dark-panel-2: #1b1d24;
  --on-dark: #f5f3ef;
  --on-dark-soft: #b8bac4;
  --dark-line: #2c2e38;
  --radius: 14px;
  --serif: "Iowan Old Style", "Palatino", "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --accent: #f97a2b;
    --accent-strong: #ff8f47;
    --accent-soft: #33210f;
    --ink: #eceaf0;
    --ink-soft: #a7a9b4;
    --bg: #0f1014;
    --surface: #17181f;
    --surface-alt: #1d1f27;
    --line: #2b2d37;
    --dark-panel: #17181f;
    --dark-panel-2: #1d1f27;
    --dark-line: #2f3140;
  }
}

* { 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: var(--sans);
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

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

a { color: var(--accent-strong); }
a:hover { color: var(--accent); }

:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
  border-radius: 4px;
}

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

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

/* ---------- Header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}

.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;
  font-size: 1.15rem;
  color: var(--ink);
  text-decoration: none;
}
.brand:hover { color: var(--ink); }

.brand-glyph {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 9px;
  background: var(--dark-panel);
  color: var(--accent);
  font-family: var(--serif);
  font-style: italic;
  font-size: 1.35rem;
  line-height: 1;
}

.site-nav ul {
  display: flex;
  gap: 1.4rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-nav a {
  text-decoration: none;
  color: var(--ink-soft);
  font-weight: 500;
  font-size: 0.97rem;
}
.site-nav a:hover { color: var(--accent-strong); }

.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;
}

@media (max-width: 720px) {
  .nav-toggle { display: inline-flex; align-items: center; gap: 0.4rem; }
  .site-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--line);
    display: none;
    padding: 0.75rem 1.25rem 1rem;
  }
  .site-nav.open { display: block; }
  .site-nav ul { flex-direction: column; gap: 0.2rem; }
  .site-nav a { display: block; padding: 0.55rem 0.25rem; font-size: 1.05rem; }
}

/* ---------- Hero ---------- */

.hero {
  background:
    radial-gradient(1100px 500px at 80% -10%, rgba(242, 106, 27, 0.16), transparent 60%),
    var(--dark-panel);
  color: var(--on-dark);
  padding: 4.5rem 0 4rem;
  overflow: hidden;
}

.hero .wrap {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: 3rem;
  align-items: center;
}

.hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-strong);
  color: #ff8f47;
  margin: 0 0 1rem;
}

.hero h1 {
  font-size: clamp(2rem, 4.5vw, 3.1rem);
  line-height: 1.12;
  margin: 0 0 1.1rem;
  letter-spacing: -0.02em;
}

.hero h1 em {
  font-family: var(--serif);
  font-style: italic;
  color: #ff8f47;
}

.hero-sub {
  font-size: 1.15rem;
  color: var(--on-dark-soft);
  max-width: 34em;
  margin: 0 0 1.8rem;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  align-items: center;
  margin-bottom: 1.4rem;
}

.store-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  background: #000;
  color: #fff;
  border: 1px solid #3a3c46;
  border-radius: 12px;
  padding: 0.55rem 1.15rem 0.6rem;
  text-decoration: none;
  line-height: 1.15;
}
.store-badge:hover { border-color: var(--accent); color: #fff; }
.store-badge svg { width: 26px; height: 26px; flex: none; }
.store-badge .badge-small { display: block; font-size: 0.68rem; opacity: 0.85; }
.store-badge .badge-big { display: block; font-size: 1.12rem; font-weight: 600; }

.btn-ghost {
  display: inline-block;
  color: var(--on-dark);
  text-decoration: none;
  font-weight: 600;
  border: 1px solid var(--dark-line);
  border-radius: 12px;
  padding: 0.85rem 1.3rem;
}
.btn-ghost:hover { border-color: #ff8f47; color: #ff8f47; }

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 1.2rem;
  padding: 0;
  margin: 0;
  list-style: none;
  font-size: 0.9rem;
  color: var(--on-dark-soft);
}
.hero-meta li::before { content: "✓ "; color: #ff8f47; }

/* Formula card mock (illustration, not a screenshot) */

.hero-visual { position: relative; }

.hero-icon {
  width: 84px;
  height: 84px;
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.45);
  margin-bottom: -30px;
  position: relative;
  z-index: 2;
  margin-left: 1.5rem;
}

.formula-card {
  background: var(--dark-panel-2);
  border: 1px solid var(--dark-line);
  border-radius: var(--radius);
  padding: 1.6rem 1.5rem 1.4rem;
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.4);
}

.formula-card .fc-topic {
  font-size: 0.78rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: #ff8f47;
  margin: 0 0 0.7rem;
  font-weight: 700;
}

.formula-card .fc-eq {
  font-family: var(--serif);
  font-style: italic;
  font-size: 2rem;
  margin: 0 0 1rem;
  color: var(--on-dark);
}

.formula-card dl {
  margin: 0;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.3rem 0.9rem;
  font-size: 0.92rem;
}
.formula-card dt {
  font-family: var(--serif);
  font-style: italic;
  color: #ff8f47;
}
.formula-card dd { margin: 0; color: var(--on-dark-soft); }

.fc-note {
  margin: 0.9rem 0 0;
  font-size: 0.78rem;
  color: var(--on-dark-soft);
  opacity: 0.75;
}

@media (max-width: 860px) {
  .hero .wrap { grid-template-columns: 1fr; gap: 2.2rem; }
  .hero-visual { max-width: 420px; }
}

/* ---------- Sections ---------- */

section { padding: 4rem 0; }

.section-alt { background: var(--surface-alt); }

.section-head { max-width: 640px; margin-bottom: 2.4rem; }

.section-head h2 {
  font-size: clamp(1.6rem, 3vw, 2.15rem);
  line-height: 1.2;
  margin: 0 0 0.7rem;
  letter-spacing: -0.015em;
}

.section-head p { color: var(--ink-soft); margin: 0; }

.eyebrow {
  display: block;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--accent-strong);
  margin-bottom: 0.6rem;
}

/* Problem / solution */

.split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
}
@media (max-width: 780px) { .split { grid-template-columns: 1fr; } }

.panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.8rem 1.7rem;
}

.panel h3 { margin: 0 0 0.7rem; font-size: 1.2rem; }
.panel p { margin: 0 0 0.8rem; color: var(--ink-soft); }
.panel p:last-child { margin-bottom: 0; }

.panel-problem { border-top: 4px solid var(--ink-soft); }
.panel-solution { border-top: 4px solid var(--accent); }

/* Features */

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.4rem;
}
@media (max-width: 960px) { .feature-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 620px) { .feature-grid { grid-template-columns: 1fr; } }

.feature {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem 1.4rem;
}

.feature .f-glyph {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 11px;
  background: var(--accent-soft);
  color: var(--accent-strong);
  font-family: var(--serif);
  font-style: italic;
  font-size: 1.3rem;
  margin-bottom: 0.9rem;
}

.feature h3 { margin: 0 0 0.45rem; font-size: 1.08rem; }
.feature p { margin: 0; color: var(--ink-soft); font-size: 0.97rem; }

/* Topics strip */

.topic-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  list-style: none;
  padding: 0;
  margin: 1.6rem 0 0;
}
.topic-list li {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.4rem 1rem;
  font-size: 0.93rem;
  font-weight: 500;
}

/* How it helps */

.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.4rem;
  counter-reset: step;
}
@media (max-width: 780px) { .steps { grid-template-columns: 1fr; } }

.step {
  position: relative;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.6rem 1.4rem 1.4rem;
}
.step::before {
  counter-increment: step;
  content: counter(step);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  font-size: 0.9rem;
  margin-bottom: 0.8rem;
}
.step h3 { margin: 0 0 0.45rem; font-size: 1.05rem; }
.step p { margin: 0; color: var(--ink-soft); font-size: 0.97rem; }

/* FAQ */

.faq-list { max-width: 760px; }

.faq-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  margin-bottom: 0.8rem;
}

.faq-q {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  background: none;
  border: 0;
  font: inherit;
  font-weight: 600;
  font-size: 1.02rem;
  color: var(--ink);
  text-align: left;
  padding: 1.05rem 1.2rem;
  cursor: pointer;
}
.faq-q .faq-caret {
  flex: none;
  transition: transform 0.2s ease;
  color: var(--accent-strong);
  font-family: var(--mono);
}
.faq-q[aria-expanded="true"] .faq-caret { transform: rotate(90deg); }

.faq-a { padding: 0 1.2rem 1.1rem; color: var(--ink-soft); }
.faq-a p { margin: 0; }
.faq-a[hidden] { display: none; }

/* Guides teaser */

.guide-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.4rem;
}
@media (max-width: 780px) { .guide-cards { grid-template-columns: 1fr; } }

.guide-card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem 1.5rem 1.4rem;
  text-decoration: none;
  color: var(--ink);
}
.guide-card:hover { border-color: var(--accent); color: var(--ink); }
.guide-card h3 { margin: 0 0 0.5rem; font-size: 1.1rem; }
.guide-card p { margin: 0 0 0.8rem; color: var(--ink-soft); font-size: 0.96rem; }
.guide-card .more { color: var(--accent-strong); font-weight: 600; font-size: 0.94rem; }

/* Final CTA */

.cta-final {
  background:
    radial-gradient(900px 400px at 15% 120%, rgba(242, 106, 27, 0.18), transparent 60%),
    var(--dark-panel);
  color: var(--on-dark);
  text-align: center;
}
.cta-final h2 { font-size: clamp(1.7rem, 3.4vw, 2.3rem); margin: 0 0 0.8rem; }
.cta-final p { color: var(--on-dark-soft); max-width: 36em; margin: 0 auto 1.8rem; }
.cta-final .hero-ctas { justify-content: center; }

/* ---------- Footer ---------- */

.site-footer {
  background: var(--bg);
  border-top: 1px solid var(--line);
  padding: 2.8rem 0 2.2rem;
  font-size: 0.94rem;
  color: var(--ink-soft);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 2rem;
  margin-bottom: 1.8rem;
}
@media (max-width: 720px) { .footer-grid { grid-template-columns: 1fr; } }

.site-footer h2 { font-size: 1rem; color: var(--ink); margin: 0 0 0.7rem; }
.site-footer ul { list-style: none; padding: 0; margin: 0; }
.site-footer li { margin-bottom: 0.45rem; }
.site-footer a { color: var(--ink-soft); text-decoration: none; }
.site-footer a:hover { color: var(--accent-strong); text-decoration: underline; }

.footer-note { border-top: 1px solid var(--line); padding-top: 1.4rem; font-size: 0.88rem; }

/* ---------- Guide article pages ---------- */

.article-hero {
  background: var(--dark-panel);
  color: var(--on-dark);
  padding: 3rem 0 2.6rem;
}
.article-hero h1 {
  font-size: clamp(1.7rem, 3.6vw, 2.5rem);
  line-height: 1.18;
  margin: 0.6rem 0 0.8rem;
  max-width: 21em;
  letter-spacing: -0.015em;
}
.article-hero .lede {
  color: var(--on-dark-soft);
  font-size: 1.12rem;
  max-width: 38em;
  margin: 0;
}

.breadcrumb {
  font-size: 0.88rem;
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  color: var(--on-dark-soft);
}
.breadcrumb a { color: var(--on-dark-soft); }
.breadcrumb a:hover { color: #ff8f47; }
.breadcrumb li + li::before { content: "›"; margin-right: 0.35rem; }

.article-body {
  max-width: 720px;
  margin: 0 auto;
  padding: 3rem 1.25rem 2rem;
}
.article-body h2 { font-size: 1.5rem; margin: 2.2rem 0 0.8rem; letter-spacing: -0.01em; }
.article-body h3 { font-size: 1.15rem; margin: 1.6rem 0 0.6rem; }
.article-body p { margin: 0 0 1.1rem; }
.article-body ul, .article-body ol { margin: 0 0 1.1rem; padding-left: 1.4rem; }
.article-body li { margin-bottom: 0.4rem; }

.article-body .eq {
  font-family: var(--serif);
  font-style: italic;
  background: var(--surface-alt);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.8rem 1.1rem;
  margin: 0 0 1.1rem;
  overflow-x: auto;
  font-size: 1.12rem;
}

.article-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 0 0 1.2rem;
  font-size: 0.95rem;
}
.article-body th, .article-body td {
  border: 1px solid var(--line);
  padding: 0.55rem 0.75rem;
  text-align: left;
}
.article-body th { background: var(--surface-alt); }
.table-scroll { overflow-x: auto; margin: 0 0 1.2rem; }
.table-scroll table { margin: 0; min-width: 480px; }

.callout {
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
  border-radius: 0 10px 10px 0;
  padding: 1rem 1.2rem;
  margin: 0 0 1.2rem;
}
.callout p { margin: 0; }

.app-note {
  background: var(--surface);
  border: 1px solid var(--line);
  border-top: 4px solid var(--accent);
  border-radius: var(--radius);
  padding: 1.5rem 1.5rem 1.4rem;
  margin: 2.4rem 0 0;
}
.app-note h2 { margin-top: 0; }

.related-guides {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 1.25rem 3.5rem;
}
.related-guides h2 { font-size: 1.25rem; }
.related-guides ul { padding-left: 1.3rem; }