:root {
  --bg: #f5f6f8;
  --surface: #ffffff;
  --surface-soft: #f8f9fb;
  --ink: #152238;
  --muted: #5d6b80;
  --line: #dbe4ef;
  --accent: #2457d6;
  --accent-strong: #173eaa;
  --accent-soft: #eaf0ff;
  --warn: #8a4b06;
  --warn-bg: #fff6e6;
  --ok: #136b4a;
  --ok-bg: #e8f8f0;
  --branch: #2e4d8e;
  --branch-bg: #edf3ff;
  --max: 980px;
  --header-max: 1180px;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(20, 35, 60, .04);
  font-family: "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
  font-size: 1.03rem;
  -webkit-text-size-adjust: 100%;
}
img { max-width: 100%; height: auto; display: block; }
a {
  color: var(--accent);
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}
a:hover { color: var(--accent-strong); text-decoration-thickness: 2px; }
:focus-visible {
  outline: 3px solid rgba(36, 87, 214, .45);
  outline-offset: 3px;
  border-radius: 5px;
}
[id] { scroll-margin-top: 7.5rem; }

.skip {
  position: absolute;
  left: -999px;
  top: auto;
}
.skip:focus {
  left: 1rem;
  top: 1rem;
  z-index: 100;
  background: var(--surface);
  color: var(--accent-strong);
  padding: .6rem .8rem;
  border: 2px solid var(--accent);
  border-radius: 10px;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: #fff;
  border-bottom: 1px solid var(--line);
}
.site-header-inner {
  max-width: var(--header-max);
  margin: 0 auto;
  padding: .8rem 1.35rem;
  display: flex;
  align-items: center;
  gap: 1rem 1.6rem;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: .7rem;
  flex: 0 0 auto;
  color: var(--ink);
  font-size: .98rem;
  font-weight: 750;
  letter-spacing: -.02em;
  text-decoration: none;
  white-space: nowrap;
}
.brand::before {
  content: "";
  width: 1.85rem;
  height: 1.85rem;
  display: inline-block;
  border-radius: 4px;
  background: var(--accent);
}
.brand:hover { color: var(--accent); }
.nav {
  min-width: 0;
  flex: 1 1 auto;
  display: flex;
  justify-content: flex-start;
  gap: .2rem;
  overflow-x: auto;
  scrollbar-width: none;
}
.nav::-webkit-scrollbar { display: none; }
.nav a {
  flex: 0 0 auto;
  color: var(--muted);
  padding: .42rem .6rem;
  border-radius: 9px;
  font-size: .87rem;
  line-height: 1.2;
  text-decoration: none;
  white-space: nowrap;
}
.nav a:hover, .nav a[aria-current="page"] {
  color: var(--accent-strong);
  background: var(--accent-soft);
}

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.5rem 1.1rem 4rem;
}
.breadcrumb {
  margin: 0 0 1rem;
  color: var(--muted);
  font-size: .82rem;
  font-weight: 650;
  letter-spacing: .04em;
  text-transform: uppercase;
}
.breadcrumb a {
  color: var(--muted);
  text-decoration: none;
}
.breadcrumb a:hover { color: var(--accent); }

.hero {
  position: relative;
  overflow: hidden;
  margin-bottom: 1rem;
  padding: 2.75rem 3rem 2.6rem;
  color: var(--ink);
  background: var(--accent-soft);
  border: 1px solid #cbd9f7;
  border-radius: 12px;
  box-shadow: none;
}
.hero h1 {
  position: relative;
  z-index: 1;
  max-width: 850px;
  margin: 0 0 .8rem;
  color: var(--ink);
  font-size: clamp(2rem, 5vw, 3.25rem);
  line-height: 1.08;
  letter-spacing: -.045em;
}
.lede {
  position: relative;
  z-index: 1;
  max-width: 800px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(1.03rem, 2vw, 1.18rem);
  line-height: 1.65;
}

.toc {
  display: grid;
  grid-template-columns: 8.5rem 1fr;
  gap: 1rem 1.5rem;
  align-items: start;
  margin: 0 0 1rem;
  padding: 1.15rem 1.35rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 16px;
}
.toc h2 {
  margin: .18rem 0 0;
  color: var(--muted);
  font-size: .78rem;
  font-weight: 750;
  letter-spacing: .09em;
  text-transform: uppercase;
}
.toc ol {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: .35rem .9rem;
  margin: 0;
  padding: 0 0 0 1.35rem;
  list-style: decimal;
}
.toc li { min-width: 0; }
.toc a { font-size: .9rem; }

.callout {
  margin: 1rem 0;
  padding: 1rem 1.15rem 1rem 1.3rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  box-shadow: none;
}
.callout strong { display: block; margin-bottom: .22rem; color: inherit; }
.callout.warn { color: var(--warn); background: var(--warn-bg); border-color: #f1d9ae; }
.callout.branch { color: var(--branch); background: var(--branch-bg); border-color: #cbd9f7; }
.callout.ok { color: var(--ok); background: var(--ok-bg); border-color: #bee6d2; }

section.step,
.faq,
.sources,
.symptom-map {
  margin: 0 0 1rem;
  padding: 1.65rem 1.8rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: none;
}
section.step h2,
.faq h2,
.sources h2,
.symptom-map h2 {
  margin: 0 0 .9rem;
  font-size: clamp(1.2rem, 2.2vw, 1.45rem);
  line-height: 1.25;
  letter-spacing: -.025em;
}
section.step h2 {
  padding-left: 0;
}
section.step h3 { margin: 1.2rem 0 .45rem; font-size: 1.05rem; }
section.step p { margin: .55rem 0; }
section.step ul, section.step ol { margin: .55rem 0 .8rem; padding-left: 1.35rem; }
section.step li { margin: .35rem 0; padding-left: .1rem; }
section.step li::marker { color: #8192ab; }
code {
  padding: .12rem .34rem;
  color: #233d67;
  background: #edf2f8;
  border: 1px solid #dfe7f1;
  border-radius: 5px;
  font-size: .9em;
}

.figure {
  margin: 1.15rem 0 .2rem;
  padding: .65rem;
  background: var(--surface-soft);
  border: 1px solid var(--line);
  border-radius: 14px;
}
.figure img { width: 100%; border-radius: 9px; background: #fff; }
.figure figcaption {
  margin: .6rem .2rem .15rem;
  color: var(--muted);
  font-size: .88rem;
  line-height: 1.5;
}

.branch-box {
  display: grid;
  gap: .7rem;
  margin: 1rem 0 .25rem;
}
@media (min-width: 640px) {
  .branch-box.two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
.branch-card {
  min-height: 4.2rem;
  padding: .85rem 1rem;
  color: var(--branch);
  background: var(--branch-bg);
  border: 1px solid #cbd9f7;
  border-radius: 12px;
}
.branch-card a { font-weight: 700; }

.step-note {
  margin: 1rem 0;
  padding: .7rem .9rem;
  color: var(--muted);
  background: #f8fafc;
  border: 1px solid var(--line);
  border-radius: 8px;
  font-size: .92rem;
}

.faq details {
  border-top: 1px solid var(--line);
  padding: .85rem 0;
}
.faq details:first-of-type { border-top: 0; padding-top: 0; }
.faq details:last-of-type { padding-bottom: 0; }
.faq summary {
  cursor: pointer;
  padding-right: 1.5rem;
  color: var(--ink);
  font-weight: 700;
  list-style: none;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::before {
  content: "+";
  display: inline-grid;
  place-items: center;
  width: 1.3rem;
  height: 1.3rem;
  margin-right: .5rem;
  color: var(--accent);
  background: var(--accent-soft);
  border-radius: 6px;
  font-weight: 750;
}
.faq details[open] summary::before { content: "−"; }
.faq details p { margin: .55rem 0 0 1.8rem; color: var(--muted); }

.sources ol { margin: 0; padding-left: 1.3rem; columns: 2; column-gap: 2.2rem; }
.sources li { margin: .5rem 0; break-inside: avoid; font-size: .94rem; }
.symptom-map ul {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: .5rem .8rem;
  margin: 0;
  padding: 0;
  list-style: none;
}
.symptom-map li {
  padding: .58rem .75rem;
  background: #f8faff;
  border: 1px solid #e1e9f4;
  border-radius: 9px;
}
.symptom-map li::before { content: "↗"; margin-right: .4rem; color: var(--accent); }

.site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.2rem 1.1rem 3.2rem;
  color: var(--muted);
  font-size: .88rem;
}
.site-footer p { margin: .45rem 0; }
.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: .45rem;
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
}
.footer-nav a {
  padding: .26rem .5rem;
  color: var(--muted);
  background: rgba(255, 255, 255, .58);
  border: 1px solid var(--line);
  border-radius: 7px;
  text-decoration: none;
}
.footer-nav a:hover { color: var(--accent); border-color: #b6c8e7; background: var(--accent-soft); }

@media (max-width: 900px) {
  .site-header-inner { flex-wrap: wrap; gap: .65rem 1rem; }
  .nav { flex-basis: 100%; justify-content: flex-start; }
}
@media (max-width: 700px) {
  body { font-size: 1rem; }
  [id] { scroll-margin-top: 8.5rem; }
  main { padding: 1rem .8rem 3rem; }
  .site-header-inner { padding: .7rem .8rem; }
  .brand { font-size: .94rem; }
  .nav { margin: 0 -.8rem; padding: 0 .8rem .15rem; }
  .nav a { padding: .42rem .55rem; }
  .hero { padding: 2rem 1.35rem 1.9rem; border-radius: 19px; }
  .hero h1 { font-size: clamp(1.9rem, 9vw, 2.45rem); }
  .toc { grid-template-columns: 1fr; gap: .45rem; padding: 1rem; }
  .toc ol { grid-template-columns: 1fr; gap: .4rem; }
  .toc h2 { margin: 0; }
  section.step, .faq, .sources, .symptom-map { padding: 1.25rem 1.05rem; border-radius: 15px; }
  .sources ol, .symptom-map ul { columns: auto; grid-template-columns: 1fr; }
  .site-footer { padding: .8rem .8rem 2.5rem; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}