:root {
  --blue: #1677ff;
  --blue-deep: #0c4db8;
  --ink: #1f2329;
  --muted: #646a73;
  --faint: #8f959e;
  --paper: #f5f6f8;
  --surface: #ffffff;
  --line: #e5e6eb;
  --soft: #e8f3ff;
  --header-h: 64px;
  --shell: 1240px;
  --pad: 40px;
  --gap: 28px;
  --radius: 8px;
  --font-sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  --font-serif: "Noto Serif SC", "Songti SC", serif;
  --font-lat: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
}

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

html {
  scroll-behavior: smooth;
  /* full-page scroll / scroll-snap：桌面一屏一段 */
  scroll-snap-type: y mandatory;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
}

img { display: block; }
a { color: var(--blue); text-decoration: none; }
a:hover { color: var(--blue-deep); }

:focus-visible {
  outline: 2px solid var(--blue);
  outline-offset: 3px;
}

.skip {
  position: absolute;
  left: 12px;
  top: -48px;
  z-index: 80;
  padding: 8px 12px;
  background: var(--surface);
  color: var(--ink);
}
.skip:focus { top: 12px; }

/* Shared horizontal rail: header / panels / footer */
.shell {
  width: min(var(--shell), 100%);
  margin-inline: auto;
  padding-inline: var(--pad);
}
.shell-narrow {
  max-width: 720px;
  margin-inline: auto;
  padding-inline: var(--pad);
}

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 50;
  height: var(--header-h);
  background: rgba(245, 246, 248, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
}
.site-header.is-scrolled {
  border-bottom-color: var(--line);
}
.header-row {
  display: flex;
  align-items: center;
  height: var(--header-h);
  gap: 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  flex-shrink: 0;
}
.brand:hover { color: var(--ink); }
.brand img { border-radius: 6px; }
.brand-name {
  font-family: var(--font-serif);
  font-weight: 700;
  font-size: 17px;
  letter-spacing: 0.06em;
}
.brand-lat {
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--blue);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  margin-left: auto;
}
.nav-links a {
  display: inline-flex;
  align-items: center;
  height: 36px;
  color: var(--muted);
  font-size: 14px;
}
.nav-links a:hover,
.nav-links a.is-on { color: var(--ink); }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 40px;
  padding: 0 16px;
  border-radius: var(--radius);
  font-family: inherit;
  font-size: 14px;
  font-weight: 500;
  border: 1px solid transparent;
  cursor: pointer;
  transition: background 150ms ease, color 150ms ease;
}
.btn-primary { background: var(--blue); color: #fff; }
.btn-primary:hover { background: var(--blue-deep); color: #fff; }
.btn-lg { height: 48px; padding: 0 22px; font-size: 15px; }
.header-cta { height: 36px; flex-shrink: 0; }

.text-link {
  display: inline-flex;
  align-items: center;
  height: 48px;
  color: var(--ink);
  font-size: 15px;
  border-bottom: 1px solid var(--ink);
}
.text-link:hover {
  color: var(--blue);
  border-bottom-color: var(--blue);
}

/* Panels — one viewport per snap (document scroll; no nested scrollport) */
.panel {
  box-sizing: border-box;
  min-height: 100svh;
  padding: calc(var(--header-h) + 28px) 0 40px;
  border-top: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  scroll-snap-align: start;
  scroll-snap-stop: always;
  overflow: visible;
}
.panel:not(.hero) > .shell {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.panel-alt { background: #eef1f5; }
.hero {
  border-top: 0;
  padding: var(--header-h) 0 0;
  display: flex;
  align-items: stretch;
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.85fr) minmax(0, 1.15fr);
  gap: 24px;
  align-items: center;
  min-height: calc(100svh - var(--header-h));
  padding-block: 28px 32px;
}

.hero-copy {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding-block: 16px;
  padding-right: 8px;
}
.eyebrow {
  margin: 0 0 12px;
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.2em;
  color: var(--blue);
}
.brand-mark {
  margin: 0;
  font-family: var(--font-serif);
  font-size: clamp(3.2rem, 6vw, 4.8rem);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: 0.06em;
}
.hero h1,
.sec-title {
  margin: 0;
  font-family: var(--font-serif);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: 0.02em;
}
.hero h1 {
  margin-top: 20px;
  font-size: clamp(1.35rem, 2vw, 1.65rem);
}
.lede,
.sec-lede {
  margin: 12px 0 0;
  color: var(--muted);
  font-size: 17px;
  max-width: 36em;
}
.hero-sub {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 15px;
  max-width: 34em;
  line-height: 1.6;
}
.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 20px 0 0;
  padding: 0;
  list-style: none;
}
.chip-row li {
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--ink);
  font-size: 13px;
  font-weight: 500;
}
.cta-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 20px;
  margin-top: 28px;
}

.hero-visual {
  min-height: 0;
  display: flex;
}
.app-screen {
  width: 100%;
  max-height: calc(100svh - var(--header-h) - 64px);
  padding: 20px 22px 24px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 12px;
  box-shadow: 0 12px 40px rgba(31, 35, 41, 0.08);
  overflow: auto;
}

.app-nav {
  text-align: center;
  font-size: 15px;
  font-weight: 700;
  padding: 4px 0 14px;
}
.app-steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  margin-bottom: 12px;
  font-size: 12px;
  color: var(--faint);
  text-align: center;
}
.app-steps .on {
  color: var(--blue);
  font-weight: 700;
  box-shadow: inset 0 -2px 0 var(--blue);
  padding-bottom: 6px;
}
.app-disc {
  margin: 0 0 14px;
  padding: 8px 10px;
  background: var(--soft);
  color: var(--muted);
  font-size: 12px;
  border-radius: 4px;
}
.app-k {
  margin: 0 0 8px;
  font-size: 13px;
  font-weight: 700;
}
.app-map {
  margin: 0 0 16px;
  padding: 0 0 0 18px;
  color: var(--muted);
  font-size: 13px;
}
.app-plan {
  margin-bottom: 10px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
}
.app-plan strong { display: block; font-size: 14px; }
.app-plan em {
  display: block;
  margin: 6px 0 8px;
  color: var(--muted);
  font-style: normal;
  font-size: 12px;
}
.app-plan p {
  margin: 0 0 6px;
  color: var(--muted);
  font-size: 12px;
}
.app-btn {
  display: inline-flex;
  margin-top: 6px;
  padding: 6px 12px;
  background: var(--blue);
  color: #fff;
  border-radius: 4px;
  font-size: 12px;
}
.app-plan.dim { opacity: 0.65; }
.app-bar {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
  font-size: 12px;
  color: var(--muted);
}
.app-bar-main { color: var(--blue); font-weight: 700; }

.sec-index {
  margin: 0 0 16px;
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--blue);
}
.sec-title {
  font-size: clamp(1.75rem, 3.2vw, 2.4rem);
  max-width: 18em;
}
.sec-lede { margin-top: 14px; }

.cost-block {
  margin-top: 36px;
  padding: 28px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.cost-desc {
  margin: 0 0 20px;
  color: var(--muted);
  font-size: 15px;
  max-width: 48em;
}
.cost-compare { margin-top: 0; }
.cost-num {
  margin: 8px 0 10px;
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 2.8rem);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: 0.02em;
}
.cost-num-on { color: var(--blue); }
.cost-note {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--gap);
  margin-top: 40px;
  align-items: stretch;
}
.compare-col {
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  min-height: 100%;
}
.compare-on {
  border-color: rgba(22, 119, 255, 0.35);
  box-shadow: inset 3px 0 0 var(--blue);
}
.split-k {
  margin: 0;
  font-size: 13px;
  color: var(--faint);
}
.split-t {
  margin: 8px 0 16px;
  font-family: var(--font-serif);
  font-size: 22px;
  font-weight: 700;
  line-height: 1.3;
}
.compare ul {
  margin: 0;
  padding: 0;
  list-style: none;
}
.compare li {
  position: relative;
  padding-left: 14px;
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 15px;
}
.compare li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.7em;
  width: 6px;
  height: 1px;
  background: var(--blue);
}

.rail {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 24px;
  margin: 40px 0 0;
  padding: 0;
  list-style: none;
  align-items: start;
}
.rail .n {
  display: block;
  margin-bottom: 12px;
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--blue);
}
.rail h3 {
  margin: 0 0 10px;
  font-family: var(--font-serif);
  font-size: 22px;
  font-weight: 700;
}
.rail p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.paths,
.trio,
.quartet {
  display: grid;
  gap: var(--gap);
  margin-top: 40px;
  align-items: stretch;
}
.paths { grid-template-columns: 1fr 1fr; }
.trio { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.quartet { grid-template-columns: repeat(4, minmax(0, 1fr)); margin-top: 20px; }

.path-card {
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}
.path-k {
  display: block;
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--blue);
}
.path-card strong {
  display: block;
  margin: 10px 0 12px;
  font-family: var(--font-serif);
  font-size: 22px;
  font-weight: 700;
}
.path-card p {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
}
.card-list {
  margin: 0;
  padding: 0;
  list-style: none;
}
.card-list li {
  position: relative;
  padding-left: 14px;
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 14px;
}
.card-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.7em;
  width: 6px;
  height: 1px;
  background: var(--blue);
}
.out-label {
  margin: 36px 0 0;
  font-family: var(--font-lat);
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--blue);
}

.bound-note {
  margin: 28px 0 0;
  color: var(--muted);
}

.closer {
  display: flex;
  align-items: center;
  justify-content: center;
}
.closer > .shell-narrow {
  flex: 0 1 auto;
}
.closer-inner {
  text-align: center;
  padding-block: 24px;
}
.closer-mark {
  font-size: clamp(2.4rem, 5vw, 3.6rem);
}
.closer .sec-title {
  margin-top: 12px;
  max-width: none;
  font-size: clamp(1.4rem, 2.5vw, 1.8rem);
}
.closer .sec-lede {
  margin: 12px auto 28px;
}
.closer .btn { margin-inline: auto; }

.site-footer {
  padding: 28px 0 40px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
  background: var(--paper);
  scroll-snap-align: end;
  scroll-snap-stop: always;
}
.footer-row {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px 32px;
}
.footer-row p { margin: 0; }

html.js .panel:not(.hero) {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 500ms ease, transform 500ms ease;
}
html.js .panel.is-in,
html.js .hero {
  opacity: 1;
  transform: none;
}

@media (max-width: 1100px) {
  .trio,
  .quartet {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 960px) {
  :root { --pad: 24px; --gap: 24px; }
  html { scroll-snap-type: none; }
  .nav-links { display: none; }
  .panel {
    min-height: 0;
    padding: calc(var(--header-h) + 32px) 0 56px;
    scroll-snap-align: none;
    scroll-snap-stop: normal;
  }
  .hero { padding: var(--header-h) 0 0; }
  .hero-grid {
    grid-template-columns: 1fr;
    min-height: 0;
    padding-block: 32px;
  }
  .hero-copy {
    max-width: none;
    justify-content: flex-start;
  }
  .hero-visual { min-height: 420px; }
  .compare,
  .paths,
  .rail,
  .trio,
  .quartet {
    grid-template-columns: 1fr;
  }
  .rail { grid-template-columns: 1fr 1fr; }
  .cost-block { padding: 20px; }
  .site-footer { scroll-snap-align: none; }
}

@media (max-width: 560px) {
  .rail { grid-template-columns: 1fr; }
  .cta-row { flex-direction: column; align-items: flex-start; gap: 12px; }
  .panel { padding: calc(var(--header-h) + 24px) 0 48px; }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
    scroll-snap-type: none;
  }
  .panel,
  .site-footer {
    scroll-snap-align: none;
    scroll-snap-stop: normal;
  }
  html.js .panel:not(.hero) {
    opacity: 1;
    transform: none;
    transition: none;
  }
}