:root {
  --bg: #f6f7f9;
  --card: #ffffff;
  --ink: #1a1d23;
  --muted: #5b6472;
  --line: #d8dee8;
  --accent: #0b5fff;
  --accent-soft: #e8f0ff;
  --warn: #8a4b00;
  --warn-bg: #fff4e5;
  --ok: #0d6b3c;
  --ok-bg: #e6f6ee;
  --branch: #3d2a6d;
  --branch-bg: #f3eefc;
  --max: 46rem;
  --nav-h: 3.25rem;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(16,24,40,.06), 0 8px 24px rgba(16,24,40,.06);
  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: 1.55;
  font-size: 1.05rem;
  -webkit-text-size-adjust: 100%;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--accent); text-underline-offset: 2px; }
a:hover { text-decoration-thickness: 2px; }

.skip {
  position: absolute; left: -999px; top: auto;
}
.skip:focus {
  left: 1rem; top: 1rem; z-index: 100;
  background: #fff; padding: .5rem .75rem; border-radius: 6px;
}

.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.site-header-inner {
  max-width: calc(var(--max) + 4rem);
  margin: 0 auto;
  padding: .65rem 1rem;
  display: flex; flex-wrap: wrap; gap: .75rem 1.25rem;
  align-items: center; justify-content: space-between;
}
.brand {
  font-weight: 700; color: var(--ink); text-decoration: none;
  letter-spacing: -0.02em;
}
.brand:hover { color: var(--accent); }
.nav {
  display: flex; flex-wrap: wrap; gap: .35rem .85rem;
  font-size: .92rem;
}
.nav a { color: var(--muted); text-decoration: none; }
.nav a:hover, .nav a[aria-current="page"] { color: var(--accent); }

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.25rem 1rem 3rem;
}
.hero {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.25rem 1.25rem 1.1rem;
  margin-bottom: 1.25rem;
}
.hero h1 {
  margin: 0 0 .65rem;
  font-size: clamp(1.55rem, 4vw, 2rem);
  line-height: 1.2;
  letter-spacing: -0.03em;
}
.lede { margin: 0; color: var(--muted); font-size: 1.05rem; }

.callout {
  border-radius: var(--radius);
  padding: .9rem 1rem;
  margin: 1rem 0 1.25rem;
  border: 1px solid var(--line);
}
.callout.warn { background: var(--warn-bg); border-color: #f0d2a0; color: var(--warn); }
.callout.branch { background: var(--branch-bg); border-color: #d5c8f0; color: var(--branch); }
.callout.ok { background: var(--ok-bg); border-color: #b7e4cb; color: var(--ok); }
.callout strong { display: block; margin-bottom: .25rem; color: inherit; }

.toc {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
  margin: 0 0 1.5rem;
}
.toc h2 {
  margin: 0 0 .5rem;
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: .04em;
  color: var(--muted);
}
.toc ol { margin: 0; padding-left: 1.2rem; }
.toc li { margin: .3rem 0; }

section.step {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.1rem 1.15rem 1.2rem;
  margin: 0 0 1rem;
  box-shadow: var(--shadow);
}
section.step h2 {
  margin: 0 0 .65rem;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
}
section.step h3 {
  margin: 1rem 0 .4rem;
  font-size: 1.05rem;
}
section.step p { margin: .45rem 0; }
section.step ul, section.step ol { margin: .4rem 0 .6rem; padding-left: 1.25rem; }
section.step li { margin: .25rem 0; }

.figure {
  margin: .85rem 0;
  background: #f0f3f8;
  border: 1px dashed #b7c2d4;
  border-radius: 8px;
  padding: .75rem;
}
.figure img { border-radius: 6px; background: #fff; }
.figure figcaption {
  margin-top: .45rem;
  font-size: .88rem;
  color: var(--muted);
}

.branch-box {
  display: grid;
  gap: .6rem;
  margin: .75rem 0;
}
@media (min-width: 640px) {
  .branch-box.two { grid-template-columns: 1fr 1fr; }
}
.branch-card {
  background: var(--branch-bg);
  border: 1px solid #d5c8f0;
  border-radius: 8px;
  padding: .75rem .85rem;
  color: var(--branch);
}
.branch-card a { font-weight: 600; }

.symptom-map, .faq, .sources {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.1rem 1.15rem;
  margin: 1.25rem 0 0;
}
.symptom-map h2, .faq h2, .sources h2 {
  margin: 0 0 .75rem;
  font-size: 1.2rem;
}
.symptom-map ul { margin: 0; padding-left: 1.2rem; }
.symptom-map li { margin: .35rem 0; }

.faq details {
  border-top: 1px solid var(--line);
  padding: .7rem 0;
}
.faq details:first-of-type { border-top: 0; }
.faq summary {
  cursor: pointer;
  font-weight: 600;
  list-style: none;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::before {
  content: "+ ";
  color: var(--accent);
  font-weight: 700;
}
.faq details[open] summary::before { content: "− "; }
.faq details p { margin: .45rem 0 0; color: var(--muted); }

.sources ol { margin: 0; padding-left: 1.2rem; }
.sources li { margin: .35rem 0; font-size: .95rem; }

.site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 1rem 2.5rem;
  color: var(--muted);
  font-size: .9rem;
}
.site-footer p { margin: .35rem 0; }

.breadcrumb {
  font-size: .88rem;
  color: var(--muted);
  margin: 0 0 .85rem;
}
.breadcrumb a { color: var(--muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--accent); }

.step-note {
  font-size: .92rem;
  color: var(--muted);
  border-left: 3px solid var(--accent);
  padding-left: .75rem;
  margin: .75rem 0;
}