:root {
  --paper: #f7f4ec;
  --surface: #fffdf8;
  --ink: #192420;
  --muted: #5e6964;
  --green: #1f5b46;
  --green-deep: #173f33;
  --green-soft: #dfeae2;
  --coral: #cf6049;
  --coral-soft: #f5ddd6;
  --blue: #416b80;
  --line: #cbd2cd;
  --shadow: 0 18px 46px rgba(25, 36, 32, 0.09);
  --serif: "Songti SC", "STSong", "Noto Serif CJK SC", Georgia, serif;
  --sans: "Microsoft YaHei", "PingFang SC", "Noto Sans CJK SC", Arial, sans-serif;
}

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

html {
  color-scheme: light;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  margin: 0;
  display: flex;
  flex-direction: column;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.72;
  letter-spacing: 0;
  text-rendering: optimizeLegibility;
}

main {
  flex: 1;
}

a {
  color: inherit;
  text-decoration-thickness: 1px;
  text-underline-offset: 4px;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button {
  font: inherit;
}

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

[hidden] {
  display: none !important;
}

.shell {
  width: min(1180px, calc(100% - 48px));
  margin-inline: auto;
}

.skip-link {
  position: fixed;
  z-index: 100;
  top: 12px;
  left: 12px;
  min-height: 44px;
  padding: 10px 16px;
  transform: translateY(-160%);
  background: var(--ink);
  color: #ffffff;
  border-radius: 4px;
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: relative;
  z-index: 20;
  background: rgba(247, 244, 236, 0.97);
  border-bottom: 1px solid rgba(25, 36, 32, 0.14);
}

.header-inner {
  min-height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  gap: 11px;
  color: var(--ink);
  font-family: var(--serif);
  font-size: 22px;
  font-weight: 700;
  text-decoration: none;
}

.brand-mark {
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  background: var(--green);
  color: #ffffff;
  border: 2px solid var(--green);
  border-radius: 4px;
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1;
}

.site-nav {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 6px;
}

.site-nav a,
.nav-status {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  padding: 8px 12px;
  color: #3d4944;
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
}

.site-nav a:hover,
.site-nav a[aria-current="page"] {
  color: var(--green);
  text-decoration: underline;
}

.nav-status {
  margin-left: 8px;
  min-height: 32px;
  padding: 4px 10px;
  background: var(--coral-soft);
  color: #833a2d;
  border: 1px solid #e3aa9e;
  border-radius: 4px;
}

.nav-toggle {
  min-width: 76px;
  min-height: 44px;
  display: none;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 4px;
  cursor: pointer;
}

.hero {
  padding-block: 76px 68px;
}

.eyebrow,
.section-kicker {
  margin: 0 0 14px;
  color: var(--green);
  font-size: 14px;
  font-weight: 800;
  letter-spacing: 0;
}

.eyebrow::before,
.section-kicker::before {
  content: "";
  width: 28px;
  height: 3px;
  display: inline-block;
  margin: 0 10px 4px 0;
  background: var(--coral);
}

h1,
h2,
h3,
p {
  overflow-wrap: break-word;
}

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

.keep-together {
  white-space: nowrap;
}

h1,
h2 {
  font-family: var(--serif);
}

.hero h1 {
  max-width: 900px;
  margin-bottom: 22px;
  font-size: 58px;
  line-height: 1.12;
  font-weight: 700;
}

.hero-copy {
  max-width: 760px;
  margin: 0;
  color: #46524d;
  font-size: 19px;
  line-height: 1.85;
}

.hero-actions {
  margin-top: 28px;
  display: flex;
  align-items: center;
  gap: 22px;
}

.primary-action {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 11px 18px;
  background: var(--green);
  color: #ffffff;
  border: 1px solid var(--green);
  border-radius: 4px;
  font-weight: 700;
  text-decoration: none;
}

.primary-action:hover {
  background: var(--green-deep);
  border-color: var(--green-deep);
}

.quiet-note {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.session-preview {
  margin: 54px 0 0;
  display: grid;
  grid-template-columns: minmax(0, 1.08fr) minmax(330px, 0.92fr);
  overflow: hidden;
  background: var(--surface);
  border: 1px solid #aeb9b2;
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.question-area,
.evidence-area {
  min-width: 0;
  padding: 42px;
}

.question-area {
  background: #fffefa;
}

.session-label {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 18px;
  margin-bottom: 48px;
  color: var(--blue);
  font-size: 14px;
  font-weight: 700;
}

.preview-status {
  padding: 3px 8px;
  background: var(--coral-soft);
  color: #7d392d;
  border: 1px solid #e2aaa0;
  border-radius: 4px;
  font-size: 12px;
  font-weight: 700;
}

.math-problem {
  margin: 0 0 34px;
  font-family: Georgia, "Times New Roman", var(--serif);
  font-size: 32px;
  line-height: 1.4;
}

.answer-line {
  min-height: 60px;
  display: flex;
  align-items: center;
  padding: 10px 0;
  color: #7b8580;
  border-bottom: 2px solid var(--ink);
}

.help-link {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  margin-top: 20px;
  color: var(--green);
  font-weight: 700;
  cursor: default;
}

.evidence-area {
  background: var(--green-soft);
  border-left: 1px solid #b8c9bc;
}

.evidence-area h2 {
  margin-bottom: 28px;
  font-size: 27px;
  line-height: 1.35;
}

.learning-steps {
  margin: 0;
  padding: 0;
  display: grid;
  gap: 20px;
  list-style: none;
}

.learning-steps li {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  align-items: start;
  gap: 13px;
}

.step-number {
  width: 32px;
  height: 32px;
  display: grid;
  place-items: center;
  background: var(--green);
  color: #ffffff;
  border-radius: 50%;
  font-size: 14px;
  font-weight: 800;
}

.learning-steps strong,
.learning-steps small {
  display: block;
}

.learning-steps strong {
  margin-bottom: 2px;
}

.learning-steps small {
  color: #52635b;
  font-size: 14px;
  line-height: 1.55;
}

.learning-band {
  padding-block: 78px 84px;
  background: var(--ink);
  color: #ffffff;
}

.learning-band .section-kicker {
  color: #b7d6c4;
}

.learning-band h2 {
  max-width: 720px;
  margin-bottom: 42px;
  font-size: 38px;
  line-height: 1.28;
}

.trust-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  border-top: 1px solid rgba(255, 255, 255, 0.28);
}

.trust-item {
  min-width: 0;
  padding: 30px 30px 0 0;
}

.trust-item + .trust-item {
  padding-left: 30px;
  border-left: 1px solid rgba(255, 255, 255, 0.18);
}

.trust-index {
  color: #f2a996;
  font-family: Georgia, serif;
  font-size: 15px;
  font-weight: 700;
}

.trust-item h3 {
  margin: 15px 0 12px;
  font-size: 20px;
}

.trust-item p {
  margin: 0;
  color: #cdd6d2;
  line-height: 1.75;
}

.principles {
  padding-block: 88px;
  display: grid;
  grid-template-columns: minmax(260px, 0.8fr) minmax(0, 1.2fr);
  gap: 80px;
}

.principles-heading h2 {
  margin-bottom: 0;
  font-size: 38px;
  line-height: 1.3;
}

.principles-list {
  border-top: 1px solid var(--line);
}

.principles-list article {
  display: grid;
  grid-template-columns: 210px minmax(0, 1fr);
  gap: 28px;
  padding: 26px 0;
  border-bottom: 1px solid var(--line);
}

.principles-list h3,
.principles-list p {
  margin: 0;
}

.principles-list h3 {
  font-size: 17px;
}

.principles-list p {
  color: var(--muted);
}

.company-band {
  padding-block: 64px;
  background: var(--coral-soft);
  border-top: 1px solid #e4bbb0;
}

.company-layout {
  display: grid;
  grid-template-columns: minmax(280px, 0.8fr) minmax(0, 1.2fr);
  gap: 80px;
  align-items: center;
}

.company-layout h2 {
  margin: 0;
  font-size: 30px;
  line-height: 1.4;
}

.company-copy p {
  margin: 0 0 15px;
  color: #563e38;
}

.company-copy a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  color: var(--green-deep);
  font-weight: 800;
}

.company-contact {
  margin: 22px 0 0;
  border-top: 1px solid #e4bbb0;
}

.company-contact div {
  display: grid;
  grid-template-columns: 76px minmax(0, 1fr);
  gap: 16px;
  padding: 11px 0;
  border-bottom: 1px solid #e4bbb0;
}

.company-contact dt {
  color: #765c55;
  font-size: 13px;
  font-weight: 700;
}

.company-contact dd {
  min-width: 0;
  margin: 0;
  color: #3f2c27;
  font-weight: 700;
  overflow-wrap: anywhere;
}

.company-contact a {
  min-height: 44px;
  align-items: center;
}

.document-main {
  padding-bottom: 88px;
}

.document-hero {
  padding-block: 70px 46px;
  border-bottom: 1px solid var(--line);
}

.document-hero h1,
.contact-hero h1,
.not-found h1 {
  margin-bottom: 18px;
  font-size: 48px;
  line-height: 1.2;
}

.document-lead {
  max-width: 760px;
  margin: 0;
  color: #46524d;
  font-size: 18px;
}

.document-date {
  margin: 20px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.document-layout {
  padding-top: 48px;
  display: grid;
  grid-template-columns: 250px minmax(0, 760px);
  justify-content: space-between;
  gap: 72px;
}

.document-summary {
  align-self: start;
  padding: 20px;
  background: var(--green-soft);
  border-left: 4px solid var(--green);
  border-radius: 0 6px 6px 0;
}

.document-summary strong {
  display: block;
  margin-bottom: 7px;
}

.document-summary p {
  margin: 0;
  color: #45594f;
  font-size: 14px;
}

.prose {
  max-width: 760px;
}

.prose section + section {
  margin-top: 42px;
}

.prose h2 {
  margin-bottom: 12px;
  font-family: var(--sans);
  font-size: 21px;
  line-height: 1.45;
}

.prose p {
  margin: 0 0 12px;
  color: #3f4b46;
}

.prose strong {
  color: var(--ink);
}

.prose a {
  color: var(--green);
  font-weight: 700;
}

.contact-main {
  padding-top: 76px;
}

.contact-hero {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(420px, 1.1fr);
  gap: 80px;
  align-items: start;
  padding-bottom: 80px;
}

.contact-panel {
  padding: 34px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-top: 5px solid var(--green);
  border-radius: 6px;
  box-shadow: var(--shadow);
}

.contact-label {
  margin: 0 0 8px;
  color: var(--coral);
  font-size: 14px;
  font-weight: 800;
}

.contact-panel h2 {
  margin-bottom: 24px;
  font-size: 27px;
  line-height: 1.4;
}

.contact-list {
  margin: 0 0 28px;
}

.contact-list div {
  display: grid;
  grid-template-columns: 92px minmax(0, 1fr);
  gap: 18px;
  padding: 14px 0;
  border-top: 1px solid var(--line);
}

.contact-list div:last-child {
  border-bottom: 1px solid var(--line);
}

.contact-list dt {
  color: var(--muted);
}

.contact-list dd {
  margin: 0;
  font-weight: 700;
}

.contact-list a {
  color: var(--green);
}

.contact-notice {
  padding-block: 56px 62px;
  background: #e8eef0;
  border-top: 1px solid #c8d4d8;
}

.narrow-copy {
  max-width: 760px;
}

.narrow-copy h2 {
  margin-bottom: 12px;
  font-size: 27px;
}

.narrow-copy p {
  margin: 0;
  color: #45545a;
}

.not-found {
  max-width: 760px;
  padding-block: 90px 110px;
}

.error-code {
  margin: 0 0 14px;
  color: var(--coral);
  font-family: Georgia, serif;
  font-size: 72px;
  font-weight: 700;
  line-height: 1;
}

.not-found > p:not(.error-code, .eyebrow) {
  max-width: 620px;
  margin: 0 0 28px;
  color: var(--muted);
  font-size: 18px;
}

.site-footer {
  background: #101815;
  color: #d7dfdb;
}

.footer-main {
  min-height: 108px;
  display: grid;
  grid-template-columns: 1fr auto auto;
  align-items: center;
  gap: 34px;
}

.footer-main p {
  margin: 0;
  font-size: 13px;
}

.footer-identity {
  min-width: 0;
}

.footer-contact {
  display: flex;
  flex-wrap: wrap;
  gap: 2px 16px;
  margin: 5px 0 0;
  color: #b8c6bf;
  font-size: 12px;
  font-style: normal;
  line-height: 1.6;
}

.footer-contact span {
  min-width: 0;
}

.footer-contact span:last-child {
  overflow-wrap: anywhere;
}

.footer-contact a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  color: #eef3f0;
  font-weight: 700;
}

.footer-main nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 4px 18px;
}

.footer-main a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  color: #eef3f0;
  font-size: 13px;
}

.footer-main a[aria-current="page"] {
  color: #f2a996;
}

.icp-link {
  white-space: nowrap;
}

@media (max-width: 920px) {
  .shell {
    width: min(100% - 40px, 820px);
  }

  .site-nav {
    gap: 0;
  }

  .site-nav a {
    padding-inline: 8px;
  }

  .nav-status {
    display: none;
  }

  .hero h1 {
    font-size: 50px;
  }

  .session-preview {
    grid-template-columns: 1fr;
  }

  .evidence-area {
    border-top: 1px solid #b8c9bc;
    border-left: 0;
  }

  .principles,
  .company-layout,
  .contact-hero {
    grid-template-columns: 1fr;
    gap: 42px;
  }

  .document-layout {
    grid-template-columns: 1fr;
    gap: 36px;
  }

  .document-summary {
    max-width: 760px;
  }

  .footer-main {
    grid-template-columns: 1fr;
    justify-items: center;
    gap: 4px;
    padding-block: 26px;
    text-align: center;
  }
}

@media (max-width: 760px) {
  .shell {
    width: calc(100% - 32px);
  }

  .header-inner {
    min-height: 66px;
    flex-wrap: wrap;
    gap: 0;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    width: 100%;
    padding: 8px 0 14px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2px;
  }

  .site-nav a {
    justify-content: flex-start;
    padding-inline: 10px;
    border-bottom: 1px solid var(--line);
  }

  .nav-status {
    display: inline-flex;
    justify-content: center;
    margin: 6px 0 0;
  }

  .hero {
    padding-block: 48px 50px;
  }

  .hero h1,
  .document-hero h1,
  .contact-hero h1,
  .not-found h1 {
    font-size: 40px;
  }

  .hero-copy,
  .document-lead {
    font-size: 17px;
  }

  .hero-actions {
    align-items: flex-start;
    flex-direction: column;
    gap: 12px;
  }

  .session-preview {
    margin-top: 38px;
  }

  .question-area,
  .evidence-area {
    padding: 28px 22px;
  }

  .session-label {
    margin-bottom: 34px;
  }

  .math-problem {
    font-size: 27px;
  }

  .learning-band {
    padding-block: 56px 62px;
  }

  .learning-band h2,
  .principles-heading h2 {
    font-size: 32px;
  }

  .trust-grid {
    grid-template-columns: 1fr;
  }

  .trust-item,
  .trust-item + .trust-item {
    padding: 24px 0;
    border-left: 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.18);
  }

  .principles {
    padding-block: 62px;
    gap: 34px;
  }

  .principles-list article {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  .company-band {
    padding-block: 50px;
  }

  .company-layout {
    gap: 26px;
  }

  .company-contact div {
    grid-template-columns: 1fr;
    gap: 2px;
  }

  .document-main {
    padding-bottom: 64px;
  }

  .document-hero {
    padding-block: 48px 34px;
  }

  .document-layout {
    padding-top: 32px;
  }

  .prose section + section {
    margin-top: 34px;
  }

  .contact-main {
    padding-top: 50px;
  }

  .contact-hero {
    padding-bottom: 58px;
  }

  .contact-panel {
    padding: 26px 20px;
  }

  .contact-list div {
    grid-template-columns: 1fr;
    gap: 2px;
  }

  .not-found {
    padding-block: 68px 86px;
  }

  .footer-main nav {
    max-width: 320px;
  }
}

@media (max-width: 380px) {
  .site-nav {
    grid-template-columns: 1fr;
  }

  .hero h1,
  .document-hero h1,
  .contact-hero h1,
  .not-found h1 {
    font-size: 36px;
  }

  .math-problem {
    font-size: 24px;
  }
}

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

  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}