:root {
  --ink: #2f6b5e;
  --ink-press: #245248;
  --ink-tint: #e8f1ee;
  --text-1: #1a2421;
  --text-2: #5c6b66;
  --text-3: #9aa8a2;
  --line: #ecefed;
  --paper: #ffffff;
  --page: #f7f8f7;
  --shell: 1120px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--page);
  color: var(--text-1);
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", Helvetica, Arial,
    "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  font-weight: 400;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

.shell {
  width: min(calc(100% - 64px), var(--shell));
  margin: 0 auto;
}

.site-header {
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.96);
}

.header-inner {
  display: flex;
  min-height: 72px;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  display: grid;
  width: 36px;
  height: 36px;
  place-items: center;
  border-radius: 8px;
  background: var(--ink);
  color: var(--paper);
  font-size: 17px;
  font-weight: 600;
}

.brand-name {
  font-size: 17px;
  font-weight: 600;
  letter-spacing: 0.02em;
}

.header-note {
  margin: 0;
  color: var(--text-3);
  font-size: 14px;
}

.section {
  padding: 112px 0;
}

.section--paper {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: var(--paper);
}

.section--tint {
  background: var(--ink-tint);
}

.hero {
  padding-top: 104px;
  padding-bottom: 120px;
}

.hero-grid {
  display: block;
}

.hero-copy {
  max-width: 880px;
}

.eyebrow {
  margin-bottom: 18px;
  color: var(--ink);
  font-size: 16px;
  font-weight: 600;
  letter-spacing: 0.12em;
}

h1 {
  max-width: 760px;
  margin-bottom: 30px;
  font-size: clamp(48px, 6vw, 76px);
  font-weight: 520;
  letter-spacing: -0.055em;
  line-height: 1.14;
}

.hero-lead {
  max-width: 820px;
  margin-bottom: 34px;
  color: var(--text-2);
  font-size: 19px;
  line-height: 1.9;
}

.hero-facts {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.hero-facts span,
.status-tag {
  border: 1px solid #c9ddd6;
  border-radius: 6px;
  background: var(--ink-tint);
  color: var(--ink);
}

.hero-facts span {
  padding: 7px 11px;
  font-size: 13px;
}

.intro-grid,
.status-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: 100px;
}

.section-title {
  margin-bottom: 0;
  font-size: clamp(32px, 4vw, 48px);
  font-weight: 520;
  letter-spacing: -0.035em;
  line-height: 1.28;
}

.intro-copy {
  padding-top: 40px;
}

.intro-copy p,
.section-body,
.status-copy {
  color: var(--text-2);
  font-size: 17px;
  line-height: 1.95;
}

.intro-copy p:last-child {
  margin-bottom: 0;
}

.section-heading {
  max-width: 800px;
  margin-bottom: 58px;
}

.section-heading--narrow {
  max-width: 700px;
}

.mode-list {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.mode-card {
  min-height: 280px;
  padding: 34px 34px 40px;
  border-right: 1px solid var(--line);
}

.mode-card:last-child {
  border-right: 0;
}

.mode-number {
  display: block;
  margin-bottom: 50px;
  color: var(--ink);
  font-size: 13px;
  font-weight: 600;
}

.mode-card h3 {
  margin-bottom: 12px;
  font-size: 22px;
  font-weight: 550;
}

.mode-card p {
  margin-bottom: 0;
  color: var(--text-2);
  font-size: 15px;
  line-height: 1.85;
}

.explanation-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.86fr) minmax(420px, 1.14fr);
  align-items: center;
  gap: 96px;
}

.section-body {
  margin-top: 28px;
  margin-bottom: 34px;
}

.feature-list {
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--line);
  list-style: none;
}

.feature-list li {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 16px;
  padding: 17px 0;
  border-bottom: 1px solid var(--line);
  color: var(--text-2);
  font-size: 14px;
}

.feature-list span {
  color: var(--ink);
  font-size: 12px;
  font-weight: 600;
}

.reading-demo {
  padding: 30px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--page);
}

.demo-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-bottom: 18px;
  border-bottom: 1px solid var(--line);
  font-size: 15px;
  font-weight: 550;
}

.status-tag {
  padding: 4px 8px;
  font-size: 11px;
  font-weight: 500;
}

.demo-kicker {
  margin: 28px 0 12px;
  color: var(--text-3);
  font-size: 12px;
  letter-spacing: 0.08em;
}

.demo-article {
  margin-bottom: 26px;
  color: var(--text-1);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 18px;
  line-height: 1.9;
}

.evidence-note {
  padding: 20px;
  border-left: 3px solid var(--ink);
  background: var(--paper);
}

.evidence-note span {
  color: var(--ink);
  font-size: 12px;
  font-weight: 600;
}

.evidence-note p {
  margin: 8px 0 0;
  color: var(--text-2);
  font-size: 14px;
  line-height: 1.8;
}

.learning-loop {
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--line);
  list-style: none;
}

.learning-loop li {
  display: grid;
  grid-template-columns: 80px minmax(0, 1fr);
  padding: 28px 0;
  border-bottom: 1px solid var(--line);
}

.learning-loop > li > span {
  color: var(--ink);
  font-size: 13px;
  font-weight: 600;
}

.learning-loop div {
  display: grid;
  grid-template-columns: minmax(160px, 0.35fr) minmax(0, 0.65fr);
  gap: 40px;
}

.learning-loop strong {
  font-size: 19px;
  font-weight: 550;
}

.learning-loop p {
  margin: 0;
  color: var(--text-2);
  font-size: 15px;
}

.ai-grid {
  display: grid;
  grid-template-columns: minmax(0, 0.85fr) minmax(0, 1.15fr);
  gap: 96px;
}

.ai-principles {
  display: grid;
  grid-template-columns: 1fr;
  border-top: 1px solid #c9ddd6;
}

.ai-principles > div {
  display: grid;
  grid-template-columns: minmax(160px, 0.35fr) minmax(0, 0.65fr);
  gap: 28px;
  padding: 22px 0;
  border-bottom: 1px solid #c9ddd6;
}

.ai-principles strong {
  font-size: 15px;
  font-weight: 550;
}

.ai-principles p {
  margin: 0;
  color: var(--text-2);
  font-size: 14px;
}

.product-status {
  background: var(--text-1);
  color: var(--paper);
}

.product-status .eyebrow {
  color: #a9c8bd;
}

.status-copy {
  margin: 42px 0 0;
  color: #c3ccc9;
}

.site-footer {
  padding: 48px 0;
  border-top: 1px solid var(--line);
  background: var(--paper);
}

.footer-inner {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 40px;
}

.footer-inner strong {
  font-size: 16px;
  font-weight: 600;
}

.footer-inner p {
  margin: 7px 0 0;
  color: var(--text-2);
  font-size: 13px;
}

.footer-meta {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  color: var(--text-3);
  font-size: 12px;
}

.footer-meta a {
  color: inherit;
  text-decoration: none;
}

.footer-meta a:hover {
  text-decoration: underline;
}

@media (max-width: 900px) {
  .section {
    padding: 88px 0;
  }

  .explanation-grid,
  .ai-grid {
    grid-template-columns: 1fr;
    gap: 64px;
  }

  .reading-demo {
    width: min(100%, 640px);
  }

  .intro-grid,
  .status-grid {
    gap: 56px;
  }

  .mode-card {
    padding-right: 24px;
    padding-left: 24px;
  }

  .ai-principles > div {
    grid-template-columns: 180px 1fr;
  }
}

@media (max-width: 640px) {
  .shell {
    width: min(calc(100% - 40px), var(--shell));
  }

  .header-inner {
    min-height: 64px;
  }

  .header-note {
    display: none;
  }

  .brand-mark {
    width: 32px;
    height: 32px;
    font-size: 15px;
  }

  .section,
  .hero {
    padding: 72px 0;
  }

  .hero {
    padding-top: 64px;
  }

  .explanation-grid,
  .ai-grid {
    gap: 48px;
  }

  .eyebrow {
    margin-bottom: 14px;
    font-size: 14px;
  }

  h1 {
    margin-bottom: 24px;
    font-size: 42px;
    letter-spacing: -0.045em;
  }

  .hero-lead {
    font-size: 16px;
    line-height: 1.85;
  }

  .hero-facts span {
    font-size: 12px;
  }

  .reading-demo {
    padding: 20px;
    border-radius: 10px;
  }

  .intro-grid,
  .status-grid {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .section-title {
    font-size: 32px;
  }

  .intro-copy,
  .status-copy {
    padding-top: 0;
  }

  .intro-copy p,
  .section-body,
  .status-copy {
    font-size: 15px;
  }

  .section-heading {
    margin-bottom: 38px;
  }

  .mode-list {
    grid-template-columns: 1fr;
  }

  .mode-card {
    min-height: auto;
    padding: 26px 0 30px;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .mode-card:last-child {
    border-bottom: 0;
  }

  .mode-number {
    margin-bottom: 20px;
  }

  .demo-article {
    font-size: 16px;
  }

  .learning-loop li {
    grid-template-columns: 48px 1fr;
  }

  .learning-loop div {
    grid-template-columns: 1fr;
    gap: 7px;
  }

  .ai-principles > div {
    grid-template-columns: 1fr;
    gap: 7px;
  }

  .status-copy {
    margin-top: 0;
  }

  .footer-inner {
    align-items: flex-start;
    flex-direction: column;
  }

  .footer-meta {
    align-items: flex-start;
  }
}

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