:root {
  --paper: #f3eadb;
  --paper-2: #ebdeca;
  --ink: #151515;
  --muted: #5e5546;
  --acid: #b5ff6a;
  --blue: #2d46d1;
  --red: #cf4c34;
  --line: #151515;
  --card: rgba(255, 252, 245, 0.8);
  --shadow: 0 18px 40px rgba(21, 21, 21, 0.14);
  --latin-display: Impact, Haettenschweiler, "Arial Narrow Bold", sans-serif;
  --display: Impact, Haettenschweiler, "Arial Narrow Bold", sans-serif;
  --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Georgia, serif;
  --mono: "IBM Plex Mono", "SFMono-Regular", Consolas, monospace;
}

html[lang="zh-CN"] {
  --display: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --serif: "Source Han Serif SC", "Noto Serif CJK SC", "Songti SC", serif;
  --mono: "IBM Plex Mono", "SFMono-Regular", Consolas, "PingFang SC", monospace;
}

html[lang="ja"] {
  --display: "Hiragino Sans", "Yu Gothic", "YuGothic", "Noto Sans JP", sans-serif;
  --serif: "Hiragino Mincho ProN", "Yu Mincho", "Noto Serif JP", serif;
  --mono: "IBM Plex Mono", "SFMono-Regular", Consolas, "Hiragino Sans", monospace;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 15% 20%, rgba(45, 70, 209, 0.1), transparent 28%),
    radial-gradient(circle at 85% 12%, rgba(181, 255, 106, 0.22), transparent 20%),
    radial-gradient(circle at 75% 82%, rgba(207, 76, 52, 0.14), transparent 24%),
    linear-gradient(180deg, #f7f1e7 0%, var(--paper) 60%, var(--paper-2) 100%);
  font-family: var(--serif);
  min-height: 100vh;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.35;
  background-image:
    linear-gradient(rgba(21, 21, 21, 0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(21, 21, 21, 0.06) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: radial-gradient(circle at center, black 55%, transparent 100%);
}

.noise {
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.08;
  background-image:
    radial-gradient(circle at 20% 30%, #000 0.6px, transparent 0.7px),
    radial-gradient(circle at 80% 10%, #000 0.8px, transparent 1px),
    radial-gradient(circle at 50% 70%, #000 0.7px, transparent 0.9px);
  background-size: 18px 18px;
}

a {
  color: inherit;
}

.shell {
  width: min(1120px, calc(100% - 2rem));
  margin: 0 auto;
}

.site-header {
  width: min(1120px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 1rem 0 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(10px);
}

.header-controls {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.brand,
.top-nav a {
  text-decoration: none;
}

.brand {
  padding: 0.45rem 0.75rem;
  background: rgba(255, 252, 245, 0.72);
  border: 2px solid var(--line);
  box-shadow: 4px 4px 0 var(--line);
}

.product-mark {
  display: inline-block;
  font-family: var(--latin-display);
  font-size: clamp(1.15rem, 1rem + 0.8vw, 1.7rem);
  text-transform: uppercase;
  letter-spacing: 0.02em;
  line-height: 0.95;
  transform: translateY(0.04em);
}

.top-nav {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.lang-menu {
  position: relative;
}

.lang-menu summary {
  list-style: none;
  cursor: pointer;
  min-width: 5rem;
  padding: 0.62rem 2rem 0.62rem 0.85rem;
  border: 2px solid rgba(21, 21, 21, 0.15);
  background: rgba(255, 252, 245, 0.72);
  box-shadow: 3px 3px 0 rgba(21, 21, 21, 0.12);
  font-family: var(--mono);
  font-size: 0.78rem;
  text-align: left;
  letter-spacing: 0.02em;
  position: relative;
}

.lang-menu summary::-webkit-details-marker {
  display: none;
}

.lang-menu summary::after {
  content: "▾";
  position: absolute;
  right: 0.75rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.82rem;
}

.lang-menu[open] summary::after {
  content: "▴";
}

.lang-menu-list {
  position: absolute;
  right: 0;
  top: calc(100% + 0.45rem);
  min-width: 9rem;
  padding: 0.35rem;
  border: 2px solid var(--line);
  background: rgba(255, 252, 245, 0.96);
  box-shadow: 6px 6px 0 rgba(21, 21, 21, 0.14);
  display: grid;
  gap: 0.25rem;
  z-index: 30;
}

.lang-link {
  padding: 0.6rem 0.75rem;
  text-decoration: none;
  text-align: left;
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.02em;
}

.lang-link:hover,
.lang-link:focus-visible {
  background: rgba(21, 21, 21, 0.06);
}

.lang-link.is-active {
  background: var(--ink);
  color: #fff7ef;
}

.top-nav a {
  padding: 0.55rem 0.8rem;
  border: 2px solid rgba(21, 21, 21, 0.15);
  background: rgba(255, 252, 245, 0.58);
  font-family: var(--mono);
  font-size: 0.83rem;
  letter-spacing: 0.02em;
}

.hero {
  padding: 5.4rem 0 2.4rem;
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(320px, 0.9fr);
  gap: 1.4rem;
  align-items: start;
}

.eyebrow,
.panel-label,
.signal-kicker,
.stat-label,
.loop-step,
.timeline-date,
.footer-title {
  font-family: var(--mono);
  letter-spacing: 0.02em;
}

.eyebrow {
  margin: 0 0 0.8rem;
  color: var(--muted);
  font-size: 0.82rem;
}

.hero h1,
.section-heading h2,
.panel h2,
.cta-band h2 {
  font-family: var(--display);
  line-height: 1.02;
  letter-spacing: 0.01em;
  font-weight: 800;
}

.hero h1 {
  margin: 0;
  font-size: clamp(3.8rem, 10vw, 8.4rem);
  max-width: 8ch;
}

.product-title {
  font-family: var(--latin-display) !important;
  text-transform: uppercase;
  letter-spacing: 0.015em;
  line-height: 0.9 !important;
  max-width: 7.5ch;
  text-wrap: balance;
}

.lede {
  margin: 1.2rem 0 0;
  font-size: clamp(1.18rem, 1rem + 0.45vw, 1.5rem);
  max-width: 32rem;
}

.sublede,
.micro-note,
.timeline-item p,
.reason-card p,
.loop-card p,
.panel p,
.faq-list p,
.site-footer,
.checklist li {
  color: var(--muted);
  line-height: 1.65;
}

.sublede,
.micro-note {
  max-width: 38rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin: 1.6rem 0 1rem;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  min-height: 3.3rem;
  padding: 0.9rem 1.2rem;
  border: 2px solid var(--line);
  font-family: var(--mono);
  letter-spacing: 0.02em;
  box-shadow: 5px 5px 0 var(--line);
  transition: transform 180ms ease, box-shadow 180ms ease, background 180ms ease;
}

.button:hover,
.button:focus-visible,
.top-nav a:hover,
.top-nav a:focus-visible,
.faq-list summary:hover {
  transform: translate(-2px, -2px);
}

.button-primary {
  background: var(--acid);
}

.button-secondary {
  background: rgba(255, 252, 245, 0.78);
}

.hero-board {
  position: relative;
  padding: 1.35rem;
  border: 2px solid var(--line);
  background: linear-gradient(180deg, rgba(255, 252, 245, 0.92), rgba(244, 234, 218, 0.86));
  box-shadow: var(--shadow);
  transform: rotate(-1.3deg);
  display: grid;
  gap: 0.8rem;
}

.hero-board::before {
  content: "";
  display: none;
}

.badge {
  display: inline-flex;
  width: fit-content;
  padding: 0.45rem 0.7rem;
  border: 2px solid var(--line);
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.02em;
}

.badge-green {
  background: var(--acid);
}

.badge-blue {
  background: rgba(45, 70, 209, 0.12);
}

.badge-red {
  background: rgba(207, 76, 52, 0.18);
}

.stat-card {
  padding: 0.95rem 1rem;
  border: 2px solid var(--line);
  background: rgba(255, 252, 245, 0.84);
}

.stat-label {
  display: block;
  margin-bottom: 0.35rem;
  font-size: 0.72rem;
}

.signal-strip {
  margin-top: 0.8rem;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.9rem;
}

.signal-strip > div {
  padding: 1rem;
  border: 2px solid rgba(21, 21, 21, 0.12);
  background: rgba(255, 252, 245, 0.65);
}

.signal-strip p {
  margin: 0.35rem 0 0;
  font-family: var(--display);
  line-height: 1;
  font-size: clamp(1.3rem, 1rem + 1vw, 2rem);
}

.content-grid,
.strategy-grid {
  padding: 1.4rem 0 0;
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1rem;
}

.panel,
.reason-card,
.timeline-item,
.loop-card,
.faq-list details,
.cta-band {
  border: 2px solid var(--line);
  background: var(--card);
  box-shadow: var(--shadow);
}

.panel,
.reason-card,
.timeline-item,
.loop-card,
.faq-list details {
  padding: 1.25rem;
}

.panel-label {
  margin: 0 0 0.8rem;
  font-size: 0.76rem;
}

.panel h2,
.section-heading h2,
.cta-band h2 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 3.8rem);
}

.panel-large p:last-child {
  margin-bottom: 0;
}

.panel-quote {
  background: var(--blue);
  color: #f7f1e7;
  transform: rotate(1.2deg);
}

.panel-quote .panel-label,
.panel-quote blockquote {
  color: inherit;
}

.panel-quote blockquote {
  margin: 0;
  font-family: var(--display);
  font-size: clamp(1.8rem, 2.1vw, 2.6rem);
  line-height: 1.05;
}

.section-heading {
  padding: 4rem 0 1.3rem;
}

.section-heading-tight {
  padding: 0;
}

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

.reason-card:nth-child(2n) {
  transform: translateY(0.5rem);
}

.reason-card h3,
.timeline-item h3,
.loop-card h3,
.faq-list summary {
  margin: 0;
  font-family: var(--display);
  letter-spacing: 0.01em;
  line-height: 1.08;
  font-weight: 800;
}

.reason-card h3,
.timeline-item h3,
.loop-card h3 {
  font-size: 1.6rem;
}

.timeline {
  display: grid;
  gap: 1rem;
}

.timeline-item {
  display: grid;
  grid-template-columns: 180px 1fr auto;
  gap: 1rem;
  align-items: start;
}

.timeline-item a {
  font-family: var(--mono);
  font-size: 0.82rem;
  text-decoration: none;
  align-self: center;
  letter-spacing: 0.02em;
}

.split-band {
  margin-top: 4rem;
  padding: 1.25rem;
  background: rgba(21, 21, 21, 0.96);
  color: #f7f1e7;
  display: grid;
  grid-template-columns: 0.95fr 1.3fr;
  gap: 1rem;
  border: 2px solid var(--line);
  box-shadow: var(--shadow);
}

.split-band .eyebrow,
.split-band .loop-card p {
  color: rgba(247, 241, 231, 0.78);
}

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

.loop-card {
  background: rgba(247, 241, 231, 0.08);
  color: #f7f1e7;
}

.loop-step {
  display: inline-flex;
  margin-bottom: 0.7rem;
  color: var(--acid);
}

.strategy-grid {
  padding-top: 4rem;
}

.checklist {
  list-style: none;
  padding: 0;
  margin: 1rem 0 0;
  display: grid;
  gap: 0.7rem;
}

.checklist li {
  padding-left: 1.3rem;
  position: relative;
}

.checklist li::before {
  content: "+";
  position: absolute;
  left: 0;
  top: 0;
  color: var(--blue);
  font-family: var(--mono);
}

.faq-shell {
  padding-top: 4rem;
}

.faq-list {
  display: grid;
  gap: 0.8rem;
}

.faq-list details {
  background: rgba(255, 252, 245, 0.74);
}

.faq-list summary {
  list-style: none;
  cursor: pointer;
  font-size: 1.35rem;
  padding-right: 2rem;
  position: relative;
}

.faq-list summary::-webkit-details-marker {
  display: none;
}

.faq-list summary::after {
  content: "+";
  position: absolute;
  top: 0;
  right: 0;
  font-family: var(--mono);
}

.faq-list details[open] summary::after {
  content: "−";
}

.cta-band {
  margin: 4rem auto 0;
  padding: 1.3rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  background: linear-gradient(90deg, var(--acid), #e2ffc1);
}

.site-footer {
  padding: 2.5rem 0 3rem;
  margin-top: 2rem;
  border-top: 2px solid rgba(21, 21, 21, 0.12);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 1rem;
  align-items: center;
}

.footer-copy {
  max-width: 34rem;
  margin: 0.7rem 0 0;
  color: var(--muted);
  line-height: 1.65;
}

.footer-links {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem 1.25rem;
  justify-content: flex-end;
  align-items: center;
}

.footer-links a {
  text-decoration-thickness: 2px;
  text-underline-offset: 0.18em;
  font-family: var(--mono);
}

@media (max-width: 960px) {
  .hero,
  .content-grid,
  .strategy-grid,
  .split-band,
  .footer-grid,
  .timeline-item,
  .cta-band {
    grid-template-columns: 1fr;
  }

  .reason-grid,
  .loop-grid,
  .signal-strip {
    grid-template-columns: 1fr 1fr;
  }

  .footer-links {
    justify-content: flex-start;
  }

  .hero-board,
  .panel-quote {
    transform: none;
  }

  .cta-band {
    align-items: flex-start;
  }
}

@media (max-width: 680px) {
  .site-header {
    position: static;
    padding-top: 0.8rem;
    flex-direction: column;
    align-items: flex-start;
  }

  .header-controls {
    width: 100%;
    justify-content: flex-start;
  }

  .hero {
    padding-top: 2.5rem;
  }

  .product-title {
    max-width: 8ch;
  }

  .signal-strip,
  .reason-grid,
  .loop-grid {
    grid-template-columns: 1fr;
  }

  .top-nav {
    justify-content: flex-start;
  }

  .lang-menu {
    width: 100%;
  }

  .lang-menu summary {
    width: 100%;
  }

  .lang-menu-list {
    left: 0;
    right: auto;
    width: 100%;
  }

  .footer-links {
    width: 100%;
    justify-content: flex-start;
  }

  .button,
  .hero-actions {
    width: 100%;
  }

  .button {
    justify-content: center;
  }
}