:root {
  --ink: #17211f;
  --ink-soft: #53605c;
  --paper: #f7f6f1;
  --white: #ffffff;
  --line: #d9ddd7;
  --coral: #e4543d;
  --coral-dark: #bd3527;
  --green: #1e6b52;
  --yellow: #f3c651;
  --max: 1160px;
  --radius: 8px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

img {
  display: block;
  max-width: 100%;
}

a {
  color: inherit;
  text-decoration: none;
}

button {
  font: inherit;
}

.container {
  width: min(calc(100% - 48px), var(--max));
  margin: 0 auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(247, 246, 241, 0.96);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(12px);
}

.nav-shell {
  display: flex;
  min-height: 72px;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  flex: none;
  font-size: 22px;
  font-weight: 800;
}

.brand-mark {
  display: grid;
  width: 38px;
  height: 38px;
  place-items: center;
  color: var(--white);
  background: var(--coral);
  border-radius: 7px;
  font-size: 18px;
}

.brand small {
  color: var(--ink-soft);
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 26px;
  color: #35413d;
  font-size: 15px;
  font-weight: 600;
}

.nav-links a {
  position: relative;
  padding: 25px 0 22px;
}

.nav-links a::after {
  position: absolute;
  right: 0;
  bottom: 17px;
  left: 0;
  height: 2px;
  background: var(--coral);
  content: "";
  opacity: 0;
  transform: scaleX(0.4);
  transition: 160ms ease;
}

.nav-links a:hover::after,
.nav-links a.active::after {
  opacity: 1;
  transform: scaleX(1);
}

.menu-toggle {
  display: none;
  width: 42px;
  height: 42px;
  padding: 0;
  color: var(--ink);
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 7px;
  cursor: pointer;
  font-size: 22px;
  line-height: 1;
}

.hero {
  position: relative;
  display: flex;
  min-height: min(720px, calc(100vh - 72px));
  align-items: flex-end;
  overflow: hidden;
  color: var(--white);
  background: #151c1a url("hero-ai.jpg") center/cover no-repeat;
}

.hero::before {
  position: absolute;
  inset: 0;
  background: rgba(11, 18, 17, 0.58);
  content: "";
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 820px;
  padding: 110px 0 92px;
}

.kicker {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 22px;
  color: var(--yellow);
  font-size: 14px;
  font-weight: 800;
}

.kicker::before {
  width: 34px;
  height: 2px;
  background: currentColor;
  content: "";
}

.hero h1 {
  max-width: 760px;
  margin: 0;
  font-size: clamp(58px, 9vw, 108px);
  line-height: 0.96;
  letter-spacing: 0;
}

.hero h1 span {
  display: block;
  margin-top: 18px;
  color: #fff7e7;
  font-size: clamp(26px, 4.2vw, 48px);
  font-weight: 700;
  line-height: 1.18;
}

.hero p {
  max-width: 670px;
  margin: 28px 0 0;
  color: rgba(255, 255, 255, 0.86);
  font-size: 18px;
}

.hero-actions,
.page-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 34px;
}

.btn {
  display: inline-flex;
  min-height: 46px;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 10px 18px;
  border: 1px solid transparent;
  border-radius: 7px;
  font-size: 15px;
  font-weight: 750;
  transition: 160ms ease;
}

.btn-primary {
  color: var(--white);
  background: var(--coral);
}

.btn-primary:hover {
  background: var(--coral-dark);
  transform: translateY(-2px);
}

.btn-light {
  color: var(--white);
  background: rgba(255, 255, 255, 0.08);
  border-color: rgba(255, 255, 255, 0.46);
}

.btn-light:hover {
  background: rgba(255, 255, 255, 0.16);
}

.btn-outline {
  color: var(--ink);
  background: transparent;
  border-color: #9fa8a3;
}

.btn-outline:hover {
  color: var(--white);
  background: var(--green);
  border-color: var(--green);
}

.section {
  padding: 88px 0;
}

.section-white {
  background: var(--white);
}

.section-dark {
  color: var(--white);
  background: #16231f;
}

.section-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 40px;
  margin-bottom: 38px;
}

.section-label,
.meta {
  color: var(--coral-dark);
  font-size: 13px;
  font-weight: 800;
}

.section-dark .section-label {
  color: var(--yellow);
}

.section-head h2 {
  max-width: 720px;
  margin: 8px 0 0;
  font-size: clamp(30px, 4vw, 48px);
  line-height: 1.18;
  letter-spacing: 0;
}

.section-head p {
  max-width: 420px;
  margin: 0;
  color: var(--ink-soft);
}

.section-dark .section-head p {
  color: #b9c3bf;
}

.article-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 22px;
}

.article-card {
  overflow: hidden;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.article-card img {
  width: 100%;
  aspect-ratio: 16 / 10;
  object-fit: cover;
}

.article-body {
  padding: 23px;
}

.article-body h3 {
  margin: 8px 0 10px;
  font-size: 20px;
  line-height: 1.4;
}

.article-body p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 15px;
}

.read-link {
  display: inline-block;
  margin-top: 18px;
  color: var(--green);
  font-size: 14px;
  font-weight: 800;
}

.read-link:hover {
  color: var(--coral-dark);
}

.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  border-top: 1px solid #3a4944;
  border-left: 1px solid #3a4944;
}

.topic {
  min-height: 230px;
  padding: 30px;
  border-right: 1px solid #3a4944;
  border-bottom: 1px solid #3a4944;
}

.topic-num {
  color: var(--yellow);
  font-size: 13px;
  font-weight: 800;
}

.topic h3 {
  margin: 42px 0 10px;
  font-size: 22px;
}

.topic p {
  margin: 0;
  color: #b9c3bf;
  font-size: 14px;
}

.path-list {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  counter-reset: path;
}

.path-item {
  position: relative;
  min-height: 200px;
  padding: 34px 34px 28px 72px;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  counter-increment: path;
}

.path-item + .path-item {
  border-left: 1px solid var(--line);
}

.path-item::before {
  position: absolute;
  top: 34px;
  left: 24px;
  color: var(--coral-dark);
  content: "0" counter(path);
  font-size: 13px;
  font-weight: 800;
}

.path-item h3 {
  margin: 0 0 10px;
  font-size: 21px;
}

.path-item p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 15px;
}

.page-hero {
  padding: 84px 0 70px;
  background: var(--white);
  border-bottom: 1px solid var(--line);
}

.page-hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(320px, 0.9fr);
  align-items: center;
  gap: 64px;
}

.page-hero h1 {
  margin: 10px 0 20px;
  font-size: clamp(42px, 7vw, 76px);
  line-height: 1.05;
  letter-spacing: 0;
}

.page-hero p {
  max-width: 640px;
  margin: 0;
  color: var(--ink-soft);
  font-size: 18px;
}

.page-hero img {
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
  border-radius: var(--radius);
}

.feature-row {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  align-items: stretch;
  gap: 0;
  overflow: hidden;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.feature-row img {
  width: 100%;
  height: 100%;
  min-height: 390px;
  object-fit: cover;
}

.feature-copy {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 44px;
}

.feature-copy h2 {
  margin: 10px 0 18px;
  font-size: clamp(28px, 4vw, 42px);
  line-height: 1.2;
}

.feature-copy p {
  margin: 0;
  color: var(--ink-soft);
}

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

.story-row {
  display: grid;
  grid-template-columns: 160px minmax(0, 1fr) 150px;
  align-items: start;
  gap: 34px;
  padding: 28px 0;
  border-bottom: 1px solid var(--line);
}

.story-row h3 {
  margin: 0 0 7px;
  font-size: 21px;
  line-height: 1.4;
}

.story-row p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 15px;
}

.story-tag {
  color: var(--green);
  font-size: 13px;
  font-weight: 800;
}

.story-date {
  color: #7d8884;
  font-size: 13px;
  text-align: right;
}

.guide-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
}

.guide-card {
  padding: 30px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.guide-card h3 {
  margin: 30px 0 10px;
  font-size: 22px;
}

.guide-card p {
  margin: 0;
  color: var(--ink-soft);
}

.guide-card .number {
  color: var(--coral-dark);
  font-size: 13px;
  font-weight: 800;
}

.code-sample {
  overflow-x: auto;
  margin: 22px 0 0;
  padding: 20px;
  color: #e8eee9;
  background: #17211f;
  border-radius: 6px;
  font: 13px/1.7 ui-monospace, SFMono-Regular, Menlo, monospace;
  white-space: pre;
}

.resource-section + .resource-section {
  margin-top: 58px;
}

.resource-section h2 {
  margin: 0 0 20px;
  font-size: 28px;
}

.resource-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

.resource-item {
  min-height: 160px;
  padding: 24px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.resource-item h3 {
  margin: 0 0 8px;
  font-size: 18px;
}

.resource-item p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 14px;
}

.resource-item small {
  display: block;
  margin-top: 16px;
  color: var(--coral-dark);
  font-weight: 800;
}

.principles {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}

.principle {
  padding: 28px 0;
  border-top: 3px solid var(--coral);
}

.principle h3 {
  margin: 0 0 12px;
  font-size: 22px;
}

.principle p {
  margin: 0;
  color: var(--ink-soft);
}

.about-note {
  max-width: 820px;
  margin: 0;
  font-size: clamp(26px, 4vw, 44px);
  font-weight: 700;
  line-height: 1.45;
}

.about-note strong {
  color: var(--yellow);
}

.faq {
  max-width: 880px;
}

.faq details {
  padding: 22px 0;
  border-top: 1px solid var(--line);
}

.faq details:last-child {
  border-bottom: 1px solid var(--line);
}

.faq summary {
  cursor: pointer;
  font-size: 18px;
  font-weight: 750;
}

.faq p {
  max-width: 720px;
  margin: 12px 0 0;
  color: var(--ink-soft);
}

.site-footer {
  color: #d8dfdb;
  background: #111916;
}

.footer-main {
  display: grid;
  grid-template-columns: 1.2fr 1fr 1fr;
  gap: 56px;
  padding: 58px 0 46px;
}

.footer-main .brand {
  color: var(--white);
}

.footer-main p {
  max-width: 390px;
  margin: 18px 0 0;
  color: #96a49e;
  font-size: 14px;
}

.footer-group h2 {
  margin: 0 0 14px;
  color: var(--white);
  font-size: 14px;
}

.footer-group a {
  display: block;
  margin: 7px 0;
  color: #aeb9b4;
  font-size: 14px;
}

.footer-group a:hover {
  color: var(--yellow);
}

.filing {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 22px 0;
  color: #8e9c96;
  border-top: 1px solid #2b3732;
  font-size: 13px;
}

.filing a:hover {
  color: var(--white);
}

@media (max-width: 900px) {
  .menu-toggle {
    display: grid;
    place-items: center;
  }

  .nav-links {
    position: absolute;
    top: 72px;
    right: 0;
    left: 0;
    display: none;
    padding: 10px 24px 20px;
    background: var(--paper);
    border-bottom: 1px solid var(--line);
  }

  .nav-links.open {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
  }

  .nav-links a {
    padding: 12px 0;
  }

  .nav-links a::after {
    bottom: 7px;
  }

  .page-hero-grid,
  .feature-row {
    grid-template-columns: 1fr;
  }

  .page-hero-grid {
    gap: 38px;
  }

  .page-hero img {
    max-height: 420px;
  }

  .feature-row img {
    min-height: 320px;
  }

  .topic-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .article-grid,
  .resource-grid,
  .principles {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .article-grid .article-card:last-child,
  .principles .principle:last-child {
    grid-column: 1 / -1;
  }

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

  .path-item + .path-item {
    border-top: 0;
    border-left: 0;
  }

  .footer-main {
    grid-template-columns: 1fr 1fr;
  }

  .footer-intro {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .container {
    width: min(calc(100% - 32px), var(--max));
  }

  .brand small {
    display: none;
  }

  .hero {
    min-height: min(680px, calc(88svh - 72px));
  }

  .hero-content {
    padding: 86px 0 64px;
  }

  .hero h1 {
    font-size: 58px;
  }

  .hero h1 span {
    font-size: 28px;
  }

  .hero p,
  .page-hero p {
    font-size: 16px;
  }

  .section,
  .page-hero {
    padding: 64px 0;
  }

  .section-head {
    display: block;
  }

  .section-head p {
    margin-top: 16px;
  }

  .article-grid,
  .guide-grid,
  .resource-grid,
  .principles,
  .topic-grid {
    grid-template-columns: 1fr;
  }

  .article-grid .article-card:last-child,
  .principles .principle:last-child {
    grid-column: auto;
  }

  .topic {
    min-height: 190px;
  }

  .topic h3 {
    margin-top: 28px;
  }

  .page-hero-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-hero h1 {
    font-size: 46px;
  }

  .feature-copy {
    padding: 28px;
  }

  .story-row {
    grid-template-columns: 1fr;
    gap: 8px;
  }

  .story-date {
    text-align: left;
  }

  .footer-main {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .footer-intro {
    grid-column: auto;
  }

  .filing {
    align-items: flex-start;
    flex-direction: column;
    gap: 7px;
  }
}

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

  *,
  *::before,
  *::after {
    transition: none !important;
  }
}