:root {
  --ink: #1a1f1c;
  --ink-soft: #4a524c;
  --jade: #2f6b5a;
  --jade-deep: #214e42;
  --cinnabar: #b33a2b;
  --cinnabar-deep: #8f2c21;
  --paper: #f3f5f1;
  --mist: #e4ebe6;
  --gold: #b8974e;
  --line: rgba(26, 31, 28, 0.14);
  --white: #ffffff;
  --shadow: 0 18px 44px rgba(26, 31, 28, 0.12);
  --font-display: "Noto Serif SC", "Songti SC", serif;
  --font-body: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --nav-h: 72px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(900px 420px at 85% -5%, rgba(47, 107, 90, 0.12), transparent 55%),
    radial-gradient(700px 360px at 10% 0%, rgba(179, 58, 43, 0.08), transparent 50%),
    linear-gradient(180deg, #f7f8f5 0%, var(--paper) 45%, #e9efea 100%);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font: inherit; border: 0; background: none; cursor: pointer; }

.container {
  width: min(1100px, calc(100% - 2.4rem));
  margin-inline: auto;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -100px;
  z-index: 1000;
  padding: 0.7rem 1rem;
  background: var(--ink);
  color: var(--white);
}
.skip-link:focus { top: 1rem; }

.site-header {
  position: fixed;
  inset: 0 0 auto;
  z-index: 100;
  height: var(--nav-h);
  color: rgba(255, 255, 255, 0.95);
  transition: 0.35s var(--ease);
}
.site-header.is-scrolled {
  color: var(--ink);
  background: rgba(243, 245, 241, 0.94);
  backdrop-filter: blur(12px);
  box-shadow: 0 1px 0 var(--line);
}

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

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0.12em;
}
.brand-seal {
  width: 1.35rem;
  height: 1.35rem;
  border: 1.5px solid currentColor;
  display: grid;
  place-items: center;
  font-size: 0.72rem;
  font-family: var(--font-display);
  transform: rotate(-8deg);
  opacity: 0.9;
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  font-size: 0.94rem;
  letter-spacing: 0.08em;
  opacity: 0.88;
  position: relative;
}
.nav-links a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -0.35rem;
  width: 100%;
  height: 1px;
  background: var(--cinnabar);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s var(--ease);
}
.nav-links a:hover { opacity: 1; }
.nav-links a:hover::after { transform: scaleX(1); }

.nav-toggle {
  display: none;
  width: 42px;
  height: 42px;
  place-items: center;
  border: 1px solid rgba(255,255,255,0.35);
  border-radius: 8px;
  color: inherit;
}
.site-header.is-scrolled .nav-toggle {
  border-color: var(--line);
  background: rgba(255,255,255,0.65);
}
.nav-toggle span,
.nav-toggle span::before,
.nav-toggle span::after {
  display: block;
  width: 17px;
  height: 1.5px;
  background: currentColor;
  position: relative;
}
.nav-toggle span::before,
.nav-toggle span::after {
  content: "";
  position: absolute;
  left: 0;
}
.nav-toggle span::before { top: -5px; }
.nav-toggle span::after { top: 5px; }

/* Hero: full-bleed with vertical writing accent */
.hero {
  position: relative;
  min-height: 100svh;
  display: grid;
  align-items: center;
  overflow: hidden;
  color: var(--white);
}
.hero-media { position: absolute; inset: 0; }
.hero-media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  animation: drift 20s var(--ease) infinite alternate;
}
.hero-media::after {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(90deg, rgba(16, 22, 20, 0.72) 0%, rgba(16, 22, 20, 0.35) 48%, rgba(16, 22, 20, 0.55) 100%),
    linear-gradient(180deg, rgba(16, 22, 20, 0.25), rgba(16, 22, 20, 0.65));
}
.hero-frame {
  position: relative;
  z-index: 1;
  width: min(1100px, calc(100% - 2.4rem));
  margin: 0 auto;
  padding: calc(var(--nav-h) + 2.5rem) 0 4rem;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: clamp(1.2rem, 4vw, 2.8rem);
  align-items: center;
}
.hero-vtext {
  writing-mode: vertical-rl;
  font-family: var(--font-display);
  letter-spacing: 0.35em;
  font-size: 0.95rem;
  color: rgba(255,255,255,0.72);
  border-left: 1px solid rgba(255,255,255,0.25);
  padding-left: 0.85rem;
  min-height: 12rem;
}
.hero-brand {
  margin: 0 0 0.85rem;
  font-family: var(--font-display);
  font-size: clamp(2.6rem, 7vw, 4.8rem);
  letter-spacing: 0.16em;
  line-height: 1.1;
  opacity: 0;
  transform: translateY(18px);
  animation: rise 0.85s var(--ease) 0.12s forwards;
}
.hero-title {
  margin: 0 0 0.9rem;
  max-width: 16em;
  font-size: clamp(1.15rem, 2.6vw, 1.65rem);
  font-weight: 600;
  letter-spacing: 0.06em;
  opacity: 0;
  transform: translateY(18px);
  animation: rise 0.85s var(--ease) 0.28s forwards;
}
.hero-desc {
  margin: 0 0 1.6rem;
  max-width: 32em;
  color: rgba(255,255,255,0.88);
  opacity: 0;
  transform: translateY(18px);
  animation: rise 0.85s var(--ease) 0.42s forwards;
}
.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  opacity: 0;
  transform: translateY(18px);
  animation: rise 0.85s var(--ease) 0.56s forwards;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0.75rem 1.4rem;
  border-radius: 2px;
  font-size: 0.95rem;
  letter-spacing: 0.08em;
  transition: 0.25s var(--ease);
}
.btn:hover { transform: translateY(-2px); }
.btn-primary { background: var(--cinnabar); color: #fff; }
.btn-primary:hover { background: var(--cinnabar-deep); }
.btn-fast { background: var(--jade); color: #fff; }
.btn-fast:hover { background: var(--jade-deep); }
.btn-ghost {
  border: 1px solid rgba(255,255,255,0.5);
  color: #fff;
}
.btn-ghost:hover { background: rgba(255,255,255,0.08); }
.btn-solid { background: var(--jade); color: #fff; }
.btn-solid:hover { background: var(--jade-deep); }
.btn-outline {
  border: 1px solid var(--line);
  color: var(--ink);
  background: rgba(255,255,255,0.65);
}
.btn-outline:hover {
  border-color: var(--jade);
  color: var(--jade-deep);
}

.section { padding: clamp(3.8rem, 7vw, 6rem) 0; }

.chapter-head {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  align-items: end;
  margin-bottom: clamp(1.6rem, 4vw, 2.5rem);
  max-width: 42rem;
}
.chapter-no {
  font-family: var(--font-display);
  font-size: clamp(2.4rem, 5vw, 3.4rem);
  color: var(--cinnabar);
  line-height: 1;
  letter-spacing: 0.08em;
}
.chapter-head h2 {
  margin: 0 0 0.35rem;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3.2vw, 2.3rem);
  letter-spacing: 0.08em;
}
.chapter-head p { margin: 0; color: var(--ink-soft); }

/* Scroll chapter: image on right, text left with seal */
.scroll-block {
  display: grid;
  grid-template-columns: 0.95fr 1.05fr;
  gap: clamp(1.2rem, 3vw, 2.4rem);
  align-items: center;
}
.scroll-copy {
  position: relative;
  padding: 0.5rem 0;
}
.seal {
  position: absolute;
  top: -0.4rem;
  right: 0;
  width: 3.2rem;
  height: 3.2rem;
  border: 2px solid var(--cinnabar);
  color: var(--cinnabar);
  display: grid;
  place-items: center;
  font-family: var(--font-display);
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  transform: rotate(12deg);
  opacity: 0.85;
}
.scroll-copy p {
  margin: 0 0 1rem;
  color: var(--ink-soft);
}
.scroll-visual {
  overflow: hidden;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  min-height: 380px;
}
.scroll-visual img {
  width: 100%;
  height: 100%;
  min-height: 380px;
  object-fit: cover;
}

.ink-band {
  background:
    linear-gradient(180deg, rgba(228, 235, 230, 0.85), rgba(243, 245, 241, 0.95));
}

/* Vertical feature rails */
.rails {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: clamp(1.2rem, 3vw, 2rem);
}
.rails-visual {
  overflow: hidden;
  min-height: 100%;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}
.rails-visual img {
  width: 100%;
  height: 100%;
  min-height: 480px;
  object-fit: cover;
}
.rail-item {
  padding: 1.15rem 0;
  border-bottom: 1px dashed var(--line);
}
.rail-item:first-child { padding-top: 0; }
.rail-item:last-child { border-bottom: 0; padding-bottom: 0; }
.rail-item h3 {
  margin: 0 0 0.35rem;
  font-family: var(--font-display);
  font-size: 1.2rem;
  letter-spacing: 0.08em;
}
.rail-item p { margin: 0; color: var(--ink-soft); }

/* Immersion panel */
.immersion {
  position: relative;
  overflow: hidden;
  min-height: 440px;
  display: grid;
  align-items: end;
  color: #fff;
  border: 1px solid rgba(255,255,255,0.08);
  box-shadow: var(--shadow);
}
.immersion img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.immersion::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(16,22,20,0.15), rgba(16,22,20,0.82));
}
.immersion-copy {
  position: relative;
  z-index: 1;
  padding: clamp(1.4rem, 4vw, 2.6rem);
  max-width: 38rem;
}
.immersion-copy h2 {
  margin: 0 0 0.7rem;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  letter-spacing: 0.1em;
}
.immersion-copy p {
  margin: 0;
  color: rgba(255,255,255,0.9);
}

.download-scroll {
  position: relative;
  overflow: hidden;
  min-height: 320px;
  display: grid;
  align-items: center;
  color: #fff;
  box-shadow: var(--shadow);
}
.download-scroll img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.download-scroll::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(100deg, rgba(16,22,20,0.88), rgba(16,22,20,0.4));
}
.download-copy {
  position: relative;
  z-index: 1;
  padding: clamp(1.5rem, 4vw, 2.8rem);
  max-width: 34rem;
}
.download-copy h2 {
  margin: 0 0 0.65rem;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  letter-spacing: 0.1em;
}
.download-copy p {
  margin: 0 0 1.2rem;
  color: rgba(255,255,255,0.9);
}
.download-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.site-footer {
  padding: 2rem 0 2.4rem;
  border-top: 1px solid var(--line);
  background: rgba(243, 245, 241, 0.95);
}
.footer-inner {
  display: grid;
  gap: 1rem;
  color: var(--ink-soft);
  font-size: 0.9rem;
}
.seo-keywords {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 0.65rem;
}
.seo-keywords a {
  font-size: 0.8rem;
  color: var(--ink-soft);
  opacity: 0.82;
}
.seo-keywords a:hover {
  color: var(--jade-deep);
  opacity: 1;
}

.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: 0.75s var(--ease);
}
.reveal.is-visible {
  opacity: 1;
  transform: none;
}

@keyframes rise {
  to { opacity: 1; transform: none; }
}
@keyframes drift {
  from { transform: scale(1.04); }
  to { transform: scale(1.1) translate(-1%, -0.5%); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .hero-media img,
  .hero-brand,
  .hero-title,
  .hero-desc,
  .hero-actions,
  .reveal {
    animation: none !important;
    transition: none !important;
    opacity: 1 !important;
    transform: none !important;
  }
}

@media (max-width: 900px) {
  .hero-frame,
  .scroll-block,
  .rails {
    grid-template-columns: 1fr;
  }
  .hero-vtext {
    writing-mode: horizontal-tb;
    border-left: 0;
    border-bottom: 1px solid rgba(255,255,255,0.25);
    padding: 0 0 0.6rem;
    min-height: auto;
    letter-spacing: 0.2em;
  }
  .scroll-visual,
  .scroll-visual img,
  .rails-visual img {
    min-height: 260px;
  }
  .rails-visual { order: -1; max-height: 300px; }
  .seal { position: static; transform: none; margin-bottom: 0.8rem; }
}

@media (max-width: 760px) {
  :root { --nav-h: 62px; }
  .nav-toggle { display: grid; }
  .nav-links {
    position: fixed;
    inset: var(--nav-h) 1rem auto;
    display: none;
    flex-direction: column;
    gap: 0;
    padding: 0.5rem;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: rgba(243,245,241,0.98);
    color: var(--ink);
    box-shadow: var(--shadow);
  }
  .nav-links.is-open { display: flex; }
  .nav-links a {
    padding: 0.8rem;
    border-radius: 8px;
  }
  .nav-links a::after { display: none; }
  .nav-links a:hover { background: var(--mist); }
}

@media (max-width: 480px) {
  .container,
  .hero-frame { width: min(1100px, calc(100% - 1.3rem)); }
  .hero-actions,
  .download-actions { width: 100%; }
  .btn { width: 100%; }
}