:root {
  --paper: #efe8d8;
  --sheet: #f7f2e6;
  --ink: #161b26;
  --ink-soft: #4a5366;
  --line: rgba(22, 27, 38, 0.12);
  --navy: #0e1a2b;
  --navy-2: #162338;
  --cream: #fffaf0;
  --l1: #d32f2f;
  --l2: #1565c0;
  --l3: #e6a100;
  --l4: #2e7d32;
  --cta: #d32f2f;
  --cta-ink: #fffaf0;
  --focus: #1565c0;
  --radius: 0.85rem;
  --wrap: 72rem;
  --header-h: 4.35rem;
  --shadow: 0 10px 28px rgba(14, 26, 43, 0.08);
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.7;
  background-color: var(--paper);
  background-image:
    linear-gradient(rgba(22, 27, 38, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(22, 27, 38, 0.045) 1px, transparent 1px);
  background-size: 28px 28px;
}

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

a {
  color: var(--l2);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

a:hover {
  color: var(--l1);
}

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
}

.skip {
  position: absolute;
  left: 0.8rem;
  top: -3rem;
  z-index: 80;
  padding: 0.45rem 0.8rem;
  background: var(--navy);
  color: var(--cream);
  text-decoration: none;
}

.skip:focus {
  top: 0.7rem;
}

.wrap {
  width: min(100% - 2rem, var(--wrap));
  margin-inline: auto;
}

.topbar {
  background: var(--navy);
  color: #d7e2f2;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
}

.topbar-inner {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  flex-wrap: wrap;
  padding: 0.45rem 0;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  min-height: var(--header-h);
  background: rgba(247, 242, 230, 0.94);
  border-bottom: 4px solid var(--navy);
  transition: box-shadow 0.2s ease;
}

.site-header.is-scrolled {
  box-shadow: var(--shadow);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: var(--header-h);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  color: inherit;
  text-decoration: none;
  font-weight: 800;
  letter-spacing: 0.01em;
}

.brand img {
  width: 2.5rem;
  height: 2.5rem;
  object-fit: cover;
  border-radius: 50%;
  border: 3px solid var(--navy);
  background: var(--cream);
}

.brand small {
  display: block;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--ink-soft);
}

.nav-toggle {
  display: none;
  border: 2px solid var(--navy);
  background: var(--cream);
  color: var(--ink);
  padding: 0.4rem 0.7rem;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.nav-panel ul {
  display: flex;
  align-items: center;
  gap: 0.35rem 0.85rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-panel a {
  color: var(--ink);
  text-decoration: none;
  font-weight: 700;
  padding: 0.35rem 0.15rem;
  border-bottom: 3px solid transparent;
}

.nav-panel a[aria-current="page"] {
  border-bottom-color: var(--l2);
}

.nav-panel a.cta {
  background: var(--cta);
  color: var(--cta-ink);
  padding: 0.42rem 0.9rem;
  border-bottom: 0;
  border-radius: 999px;
}

.nav-panel a.cta:hover {
  color: var(--cta-ink);
  filter: brightness(1.05);
}

.metro-board {
  margin: 1.4rem 0 0;
  padding: 1.1rem 1.15rem 1.2rem;
  background: var(--cream);
  border: 2px solid var(--navy);
  box-shadow: var(--shadow);
}

.metro-board figcaption {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-bottom: 1rem;
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.metro-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem 0.9rem;
  margin: 0 0 1rem;
  padding: 0;
  list-style: none;
  font-size: 0.8rem;
  font-weight: 700;
}

.metro-legend span {
  display: inline-block;
  width: 1.15rem;
  height: 0.35rem;
  margin-right: 0.35rem;
  vertical-align: middle;
}

.metro-legend .c1 { background: var(--l1); }
.metro-legend .c2 { background: var(--l2); }
.metro-legend .c3 { background: var(--l3); }
.metro-legend .c4 { background: var(--l4); }

.metro-line {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  list-style: none;
  margin: 0;
  padding: 0.4rem 0 0;
  position: relative;
}

.metro-line::before {
  content: "";
  position: absolute;
  left: 8%;
  right: 8%;
  top: 1.15rem;
  height: 8px;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--l1) 0 25%, var(--l2) 25% 50%, var(--l3) 50% 75%, var(--l4) 75% 100%);
}

.metro-stop {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 0 0.4rem;
}

.metro-stop a {
  display: block;
  color: inherit;
  text-decoration: none;
}

.metro-ring {
  display: block;
  width: 1.35rem;
  height: 1.35rem;
  margin: 0.5rem auto 0.7rem;
  border-radius: 50%;
  background: var(--cream);
  border: 4px solid var(--navy);
  box-shadow: 0 0 0 3px var(--sheet);
}

.metro-stop[data-station="download"] .metro-ring { border-color: var(--l1); }
.metro-stop[data-station="install"] .metro-ring { border-color: var(--l2); }
.metro-stop[data-station="config"] .metro-ring { border-color: var(--l3); }
.metro-stop[data-station="update"] .metro-ring { border-color: var(--l4); }

body[data-here="download"] .metro-stop[data-station="download"],
body[data-here="install"] .metro-stop[data-station="install"],
body[data-here="config"] .metro-stop[data-station="config"],
body[data-here="update"] .metro-stop[data-station="update"],
.metro-stop.is-here {
  font-weight: 800;
}

body[data-here="download"] .metro-stop[data-station="download"] .metro-ring,
body[data-here="install"] .metro-stop[data-station="install"] .metro-ring,
body[data-here="config"] .metro-stop[data-station="config"] .metro-ring,
body[data-here="update"] .metro-stop[data-station="update"] .metro-ring,
.metro-stop.is-here .metro-ring {
  transform: scale(1.12);
  box-shadow: 0 0 0 4px var(--cream), 0 0 0 7px currentColor;
}

body[data-here="download"] .metro-stop[data-station="download"] .metro-ring,
.metro-stop[data-station="download"].is-here .metro-ring {
  background: var(--l1);
  color: var(--l1);
}

body[data-here="install"] .metro-stop[data-station="install"] .metro-ring,
.metro-stop[data-station="install"].is-here .metro-ring {
  background: var(--l2);
  color: var(--l2);
}

body[data-here="config"] .metro-stop[data-station="config"] .metro-ring,
.metro-stop[data-station="config"].is-here .metro-ring {
  background: var(--l3);
  color: var(--l3);
}

body[data-here="update"] .metro-stop[data-station="update"] .metro-ring,
.metro-stop[data-station="update"].is-here .metro-ring {
  background: var(--l4);
  color: var(--l4);
}

.metro-code {
  display: block;
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  color: var(--ink-soft);
}

.metro-name {
  display: block;
  font-size: 1.05rem;
  font-weight: 800;
}

.metro-hint {
  display: block;
  font-size: 0.78rem;
  color: var(--ink-soft);
}

.here-flag {
  display: none;
  margin-top: 0.25rem;
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  color: var(--l1);
}

body[data-here="download"] .metro-stop[data-station="download"] .here-flag,
body[data-here="install"] .metro-stop[data-station="install"] .here-flag,
body[data-here="config"] .metro-stop[data-station="config"] .here-flag,
body[data-here="update"] .metro-stop[data-station="update"] .here-flag,
.metro-stop.is-here .here-flag {
  display: inline-block;
}

.hero,
.page-hero,
section {
  padding: 2.4rem 0;
}

.hero {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 1.6rem;
  align-items: center;
}

.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}

.tag {
  display: inline-block;
  padding: 0.18rem 0.55rem;
  border: 2px solid var(--navy);
  background: var(--cream);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.04em;
}

h1,
h2,
h3 {
  line-height: 1.25;
  margin: 0 0 0.7rem;
}

h1 {
  font-size: clamp(2rem, 4vw, 3.1rem);
  letter-spacing: -0.03em;
}

h2 {
  font-size: clamp(1.4rem, 2.4vw, 1.85rem);
}

.lead {
  color: var(--ink-soft);
  font-size: 1.02rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  margin: 1.1rem 0;
}

.button,
.button-alt {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 2.7rem;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  font-weight: 800;
  text-decoration: none;
}

.button {
  background: var(--cta);
  color: var(--cta-ink);
}

.button:hover {
  color: var(--cta-ink);
  filter: brightness(1.05);
}

.button-alt {
  background: var(--cream);
  color: var(--ink);
  border: 2px solid var(--navy);
}

.button-alt:hover {
  color: var(--ink);
  background: #fff;
}

.metrics {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.7rem;
}

.metric {
  padding: 0.75rem 0.8rem;
  background: var(--cream);
  border-left: 6px solid var(--navy);
}

.metric:nth-child(1) { border-left-color: var(--l1); }
.metric:nth-child(2) { border-left-color: var(--l2); }
.metric:nth-child(3) { border-left-color: var(--l4); }

.metric strong {
  display: block;
  font-size: 1.05rem;
}

.metric span {
  color: var(--ink-soft);
  font-size: 0.86rem;
}

.hero-art {
  position: relative;
  background: var(--cream);
  border: 2px solid var(--navy);
  padding: 0.7rem;
  box-shadow: var(--shadow);
}

.hero-art img,
.figure img {
  display: block;
  width: 100%;
  border: 1px solid var(--line);
}

.map-label {
  display: flex;
  justify-content: space-between;
  margin-top: 0.45rem;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}

.section-head {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: end;
  flex-wrap: wrap;
  margin-bottom: 1.1rem;
}

.section-head p {
  max-width: 34rem;
  color: var(--ink-soft);
}

.grid-2,
.grid-3,
.grid-4 {
  display: grid;
  gap: 0.9rem;
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

.card,
.seo-card,
.platform,
.step {
  background: var(--cream);
  border: 2px solid var(--navy);
  padding: 1rem 1.05rem 1.1rem;
  box-shadow: var(--shadow);
}

.seo-card {
  color: inherit;
  text-decoration: none;
}

.seo-card:hover,
.card:focus-within {
  transform: translateY(-2px);
}

.kicker {
  display: inline-block;
  margin-bottom: 0.4rem;
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  color: var(--l2);
}

.card:nth-child(4n + 1) { border-top: 6px solid var(--l1); }
.card:nth-child(4n + 2) { border-top: 6px solid var(--l2); }
.card:nth-child(4n + 3) { border-top: 6px solid var(--l3); }
.card:nth-child(4n + 4) { border-top: 6px solid var(--l4); }

.detail {
  display: grid;
  grid-template-columns: 0.92fr 1.08fr;
  gap: 1.3rem;
  align-items: center;
}

.figure {
  background: var(--cream);
  border: 2px solid var(--navy);
  padding: 0.7rem;
}

.checklist {
  margin: 0 0 1rem;
  padding-left: 1.1rem;
}

.checklist li + li {
  margin-top: 0.4rem;
}

.faq details {
  background: var(--cream);
  border: 2px solid var(--navy);
  padding: 0.7rem 0.95rem;
  margin-bottom: 0.65rem;
}

.faq summary {
  cursor: pointer;
  font-weight: 800;
}

.faq p {
  color: var(--ink-soft);
}

.crumbs {
  font-size: 0.86rem;
  color: var(--ink-soft);
}

.warn,
.note {
  padding: 0.8rem 0.95rem;
  border-left: 6px solid var(--l3);
  background: var(--cream);
}

.warn {
  border-left-color: var(--l1);
}

footer {
  background: var(--navy);
  color: #d5deec;
  padding: 2.2rem 0 1.2rem;
}

footer a {
  color: #f3d27a;
}

footer a:hover {
  color: #fff;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.3fr 0.8fr 0.8fr 1.1fr;
  gap: 1.2rem;
}

.logo-block img {
  width: 2.2rem;
  height: 2.2rem;
}

.logo-block {
  color: #fffaf0;
  margin-bottom: 0.6rem;
}

footer h3 {
  color: #fffaf0;
  font-size: 0.95rem;
}

footer ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

footer li + li {
  margin-top: 0.35rem;
}

.legal {
  display: flex;
  justify-content: space-between;
  gap: 0.8rem;
  flex-wrap: wrap;
  margin-top: 1.4rem;
  padding-top: 0.9rem;
  border-top: 1px solid rgba(255, 250, 240, 0.16);
  font-size: 0.8rem;
}

@media (max-width: 960px) {
  .hero,
  .detail,
  .footer-grid,
  .metrics,
  .grid-4,
  .grid-3 {
    grid-template-columns: 1fr 1fr;
  }

  .metro-line {
    grid-template-columns: 1fr 1fr;
    gap: 1.1rem 0.5rem;
  }

  .metro-line::before {
    display: none;
  }
}

@media (max-width: 760px) {
  .nav-toggle {
    display: inline-flex;
  }

  .site-header {
    position: sticky;
  }

  .nav-panel {
    display: none;
    position: absolute;
    left: 1rem;
    right: 1rem;
    top: calc(100% + 0.45rem);
    background: var(--cream);
    border: 2px solid var(--navy);
    padding: 0.7rem;
    box-shadow: var(--shadow);
  }

  .nav-panel.is-open {
    display: block;
  }

  .nav-panel ul {
    flex-direction: column;
    align-items: stretch;
  }

  .hero,
  .detail,
  .footer-grid,
  .metrics,
  .grid-4,
  .grid-3,
  .grid-2,
  .metro-line {
    grid-template-columns: 1fr;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }

  .seo-card:hover,
  .card:focus-within,
  body[data-here="download"] .metro-stop[data-station="download"] .metro-ring,
  body[data-here="install"] .metro-stop[data-station="install"] .metro-ring,
  body[data-here="config"] .metro-stop[data-station="config"] .metro-ring,
  body[data-here="update"] .metro-stop[data-station="update"] .metro-ring,
  .metro-stop.is-here .metro-ring {
    transform: none;
  }
}