@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

/* ===== RESET & BASE ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --c-black: #000000;
  --c-white: #ffffff;
  --c-gray-50: #f5f5f5;
  --c-gray-100: #e8e8e8;
  --c-gray-200: #d0d0d0;
  --c-gray-500: #888888;
  --c-gray-700: #333333;
  --font-main: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --header-h: 64px;
  --subnav-h: 48px;
  --radius: 4px;
  --ease: cubic-bezier(0.16, 1, 0.3, 1);
}

html {
  font-family: var(--font-main);
  font-size: 16px;
  line-height: 1.6;
  color: var(--c-black);
  background: var(--c-white);
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  overflow-x: hidden;
}

a {
  color: var(--c-black);
  text-decoration: underline;
  text-underline-offset: 3px;
}

a:hover { opacity: 0.65; }

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

ul { list-style: none; }

/* ===== SITE WRAP ===== */
.site-wrap {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ===== HEADER ===== */
.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--header-h);
  background: var(--c-black);
  color: var(--c-white);
  z-index: 900;
  border-bottom: 1px solid #222;
}

.header-inner {
  max-width: 1400px;
  margin: 0 auto;
  height: 100%;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
}

.main-nav {
  width: 100%;
}

.main-nav > p {
  display: flex;
  align-items: center;
  gap: 0;
  flex-wrap: nowrap;
  overflow: hidden;
}

.main-nav > p > a {
  color: var(--c-white);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 400;
  padding: 0 0.9rem;
  height: var(--header-h);
  display: inline-flex;
  align-items: center;
  white-space: nowrap;
  transition: background 0.18s var(--ease);
  letter-spacing: 0.01em;
}

.main-nav > p > a:hover {
  background: #1a1a1a;
  opacity: 1;
}

.brand-link {
  font-size: 1rem !important;
  font-weight: 700 !important;
  letter-spacing: -0.02em !important;
  margin-right: auto;
  flex-shrink: 0;
}

.nav-cta {
  margin-left: auto;
  flex-shrink: 0;
  background: var(--c-white) !important;
  color: var(--c-black) !important;
  font-weight: 700 !important;
  padding: 0 1.5rem !important;
  height: 40px !important;
  align-self: center !important;
  border-radius: var(--radius);
  transition: background 0.18s var(--ease), color 0.18s !important;
}

.nav-cta:hover {
  background: var(--c-gray-100) !important;
  opacity: 1 !important;
}

/* ===== HAMBURGER / FULLSCREEN MENU ===== */
.menu-toggle {
  position: fixed;
  top: 12px;
  right: 1.5rem;
  z-index: 950;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 6px;
  padding: 8px;
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--c-white);
  transition: transform 0.25s var(--ease), opacity 0.2s;
}

.menu-toggle.is-open span:first-child {
  transform: translateY(4px) rotate(45deg);
}
.menu-toggle.is-open span:last-child {
  transform: translateY(-4px) rotate(-45deg);
}

.fullscreen-menu {
  position: fixed;
  inset: 0;
  background: var(--c-black);
  color: var(--c-white);
  z-index: 940;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s var(--ease);
}

.fullscreen-menu.is-open {
  opacity: 1;
  pointer-events: all;
}

.fullscreen-menu nav > p {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
}

.fullscreen-menu nav > p > a {
  color: var(--c-white);
  text-decoration: none;
  font-size: clamp(1.2rem, 4vw, 2rem);
  font-weight: 700;
  padding: 0.75rem 2rem;
  display: block;
  text-align: center;
  letter-spacing: -0.02em;
  transition: opacity 0.15s;
  min-height: 40px;
  line-height: 1.2;
}

.fullscreen-menu nav > p > a:hover { opacity: 0.5; }

.menu-close {
  position: absolute;
  top: 1rem;
  right: 1.5rem;
  background: none;
  border: none;
  color: var(--c-white);
  font-size: 1.5rem;
  cursor: pointer;
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* ===== STICKY SUBNAV ===== */
.sticky-subnav {
  position: sticky;
  top: var(--header-h);
  z-index: 800;
  background: var(--c-white);
  border-bottom: 2px solid var(--c-black);
  height: var(--subnav-h);
  overflow: hidden;
}

.sticky-subnav nav > p {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 1.5rem;
  height: var(--subnav-h);
  display: flex;
  align-items: center;
  gap: 0;
  overflow-x: auto;
  scrollbar-width: none;
}

.sticky-subnav nav > p::-webkit-scrollbar { display: none; }

.sticky-subnav nav > p > a {
  text-decoration: none;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--c-gray-500);
  padding: 0 1rem;
  height: var(--subnav-h);
  display: inline-flex;
  align-items: center;
  white-space: nowrap;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: color 0.18s, border-color 0.18s;
}

.sticky-subnav nav > p > a:hover,
.sticky-subnav nav > p > a.active {
  color: var(--c-black);
  border-bottom-color: var(--c-black);
}

/* ===== MAIN LAYOUT (with header offset) ===== */
main {
  flex: 1;
  margin-top: var(--header-h);
}

/* ===== HERO (HOME) ===== */
.hero-section {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  padding: 8rem 1.5rem 6rem;
  max-width: 1400px;
  margin: 0 auto;
  position: relative;
}

.hero-content {
  position: relative;
  z-index: 2;
}

.hero-h1 {
  font-size: clamp(3rem, 10vw, 12rem);
  font-weight: 900;
  letter-spacing: -0.05em;
  line-height: 0.92;
  color: var(--c-black);
  margin-bottom: 2rem;
  word-break: break-all;
}

.hero-lead {
  font-size: clamp(1rem, 2.5vw, 1.4rem);
  font-weight: 300;
  color: var(--c-gray-700);
  max-width: 600px;
  margin-bottom: 3rem;
  line-height: 1.7;
}

.hero-btn {
  display: inline-block;
  background: var(--c-black);
  color: var(--c-white);
  text-decoration: none;
  font-weight: 700;
  font-size: 1rem;
  padding: 1rem 2.5rem;
  border-radius: var(--radius);
  letter-spacing: 0.03em;
  transition: background 0.2s var(--ease);
  min-height: 48px;
  line-height: 1.4;
}

.hero-btn:hover { background: var(--c-gray-700); opacity: 1; }

.hero-media {
  margin-top: 3rem;
}

.hero-img {
  width: 100%;
  max-height: 40vh;
  object-fit: cover;
  border-radius: var(--radius);
}

/* ===== INNER HERO ===== */
.inner-hero {
  padding: 6rem 1.5rem 5rem;
  max-width: 1400px;
  margin: 0 auto;
  border-bottom: 1px solid var(--c-gray-100);
}

.inner-hero-content {
  max-width: 860px;
}

.inner-hero h1 {
  font-size: clamp(2rem, 6vw, 5rem);
  font-weight: 900;
  letter-spacing: -0.04em;
  line-height: 1.0;
  margin-bottom: 1.25rem;
  color: var(--c-black);
}

.inner-hero--narrow {
  padding: 4rem 1.5rem 3rem;
}

/* ===== FEATURE HERO ===== */
.feature-hero {
  padding: 6rem 1.5rem 5rem;
  max-width: 1400px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: center;
  border-bottom: 1px solid var(--c-gray-100);
}

.feature-hero-text h1 {
  font-size: clamp(2rem, 5vw, 4rem);
  font-weight: 900;
  letter-spacing: -0.04em;
  line-height: 1.05;
  margin-bottom: 1.25rem;
}

.feature-img {
  width: 100%;
  border-radius: var(--radius);
  object-fit: cover;
}

/* ===== ABOUT HERO ===== */
.about-hero {
  padding: 7rem 1.5rem 6rem;
  max-width: 1400px;
  margin: 0 auto;
  border-bottom: 3px solid var(--c-black);
}

.about-hero-text h1 {
  font-size: clamp(2.5rem, 7vw, 7rem);
  font-weight: 900;
  letter-spacing: -0.05em;
  line-height: 0.95;
  margin-bottom: 1.5rem;
}

/* ===== EYEBROW ===== */
.eyebrow {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--c-gray-500);
  border: 1px solid var(--c-gray-200);
  padding: 0.3em 0.8em;
  border-radius: 2px;
  margin-bottom: 1.5rem;
}

/* ===== SUBTITLE PATTERN ===== */
.subtitle {
  font-size: 1rem;
  font-weight: 300;
  color: var(--c-gray-700);
  line-height: 1.6;
  margin-bottom: 1.5rem;
}

/* ===== META DATES ===== */
.meta-dates {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin-top: 0.75rem;
}

.pub-date, .mod-date {
  font-size: 0.82rem;
  color: var(--c-gray-500);
  font-weight: 400;
}

/* ===== CONTENT SECTION ===== */
.content-section {
  max-width: 1400px;
  margin: 0 auto;
  padding: 4rem 1.5rem 6rem;
}

.page-content {
  padding-top: 3rem;
}

/* ===== CONTENT WITH ASIDE ===== */
.content-with-aside {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 4rem;
  align-items: start;
}

/* ===== MAIN CONTENT / PROSE ===== */
.main-content {
  min-width: 0;
}

.prose h2 {
  font-size: clamp(1.4rem, 3vw, 2.2rem);
  font-weight: 900;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin: 3rem 0 0.6rem;
  color: var(--c-black);
}

.prose h2:first-child { margin-top: 0; }

.prose h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin: 2rem 0 0.5rem;
  color: var(--c-black);
}

.prose p {
  font-size: 1rem;
  line-height: 1.75;
  margin-bottom: 1.25rem;
  color: var(--c-gray-700);
}

.prose ul, .prose ol {
  list-style: disc;
  padding-left: 1.5rem;
  margin-bottom: 1.25rem;
}

.prose ol { list-style: decimal; }

.prose li {
  font-size: 1rem;
  line-height: 1.75;
  margin-bottom: 0.4rem;
  color: var(--c-gray-700);
}

.prose a {
  color: var(--c-black);
  font-weight: 500;
}

.prose blockquote {
  border-left: 4px solid var(--c-black);
  padding: 0.75rem 1.5rem;
  margin: 1.5rem 0;
  background: var(--c-gray-50);
}

.prose blockquote p { margin-bottom: 0; }

.prose code {
  font-family: 'Courier New', monospace;
  font-size: 0.9em;
  background: var(--c-gray-100);
  padding: 0.1em 0.4em;
  border-radius: 2px;
}

.prose pre {
  background: var(--c-black);
  color: var(--c-white);
  padding: 1.5rem;
  border-radius: var(--radius);
  overflow-x: auto;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
  line-height: 1.6;
}

.prose--legal h2 { font-size: 1.4rem; margin-top: 2.5rem; }
.prose--legal p { font-size: 0.95rem; color: var(--c-gray-700); }

/* ===== SIDEBAR / ASIDE ===== */
.sidebar {
  position: sticky;
  top: calc(var(--header-h) + 2rem);
  background: var(--c-gray-50);
  border-radius: var(--radius);
  padding: 1.75rem;
  border: 1px solid var(--c-gray-100);
}

.sidebar h2 {
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--c-black);
  margin-bottom: 0.25rem;
}

.sidebar .subtitle {
  font-size: 0.8rem;
  margin-bottom: 1rem;
}

.sidebar ul {
  margin-bottom: 1.5rem;
}

.sidebar ul li {
  border-bottom: 1px solid var(--c-gray-100);
}

.sidebar ul li:last-child { border-bottom: none; }

.sidebar ul li a {
  display: block;
  padding: 0.55rem 0;
  font-size: 0.88rem;
  color: var(--c-gray-700);
  text-decoration: none;
  font-weight: 400;
  transition: color 0.15s, padding-left 0.15s;
}

.sidebar ul li a:hover,
.sidebar ul li a[aria-current="page"] {
  color: var(--c-black);
  padding-left: 0.4rem;
  font-weight: 500;
}

.aside-cta {
  margin-top: 0.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--c-gray-200);
}

.cta-link {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--c-black);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  padding: 0.5rem 0;
  min-height: 40px;
  transition: opacity 0.15s;
}

.cta-link:hover { opacity: 0.6; }

/* ===== CARDS SECTION ===== */
.cards-section {
  max-width: 1400px;
  margin: 0 auto;
  padding: 3rem 1.5rem 5rem;
  border-top: 1px solid var(--c-gray-100);
}

.cards-section h2 {
  font-size: clamp(1.8rem, 4vw, 3.5rem);
  font-weight: 900;
  letter-spacing: -0.04em;
  margin-bottom: 0.4rem;
  line-height: 1.1;
}

.card-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-top: 2.5rem;
}

.card-list li article {
  background: var(--c-gray-50);
  border-radius: var(--radius);
  padding: 2rem 1.75rem;
  height: 100%;
  transition: transform 0.2s var(--ease), background 0.2s;
}

.card-list li article:hover {
  transform: translateY(-3px);
  background: var(--c-gray-100);
}

.card-list li article h3 {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 0.65rem;
  line-height: 1.35;
}

.card-list li article h3 a {
  color: var(--c-black);
  text-decoration: none;
}

.card-list li article h3 a:hover { opacity: 0.7; }

.card-list li article p {
  font-size: 0.9rem;
  color: var(--c-gray-500);
  line-height: 1.6;
  font-weight: 300;
}

/* ===== CTA SECTION ===== */
.cta-section {
  max-width: 1400px;
  margin: 0 auto;
  padding: 5rem 1.5rem 6rem;
  border-top: 1px solid var(--c-gray-100);
}

.cta-section h2 {
  font-size: clamp(2rem, 5vw, 5rem);
  font-weight: 900;
  letter-spacing: -0.04em;
  line-height: 1.0;
  margin-bottom: 0.4rem;
}

.cta-section .cta-link {
  font-size: 1.1rem;
  margin-top: 1rem;
  min-height: 48px;
}

/* ===== FAQ CONTENT ===== */
.faq-content details {
  border-bottom: 1px solid var(--c-gray-100);
  padding: 1.25rem 0;
}

.faq-content summary {
  font-size: 1.05rem;
  font-weight: 700;
  cursor: pointer;
  padding: 0.25rem 0;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  min-height: 40px;
}

.faq-content summary::-webkit-details-marker { display: none; }
.faq-content summary::after {
  content: '+';
  font-size: 1.3rem;
  font-weight: 300;
  flex-shrink: 0;
  line-height: 1;
  color: var(--c-gray-500);
}

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

.faq-content details > *:not(summary) {
  padding-top: 0.75rem;
}

/* ===== FOOTER ===== */
.site-footer {
  background: var(--c-black);
  color: var(--c-white);
  margin-top: auto;
}

.footer-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 4rem 1.5rem 3rem;
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: 3rem;
}

.footer-col address {
  font-style: normal;
  font-size: 0.92rem;
  line-height: 1.7;
  color: var(--c-gray-200);
}

.footer-col address strong {
  color: var(--c-white);
  font-size: 1rem;
  font-weight: 700;
  display: block;
  margin-bottom: 0.5rem;
}

.footer-col ul li a {
  color: var(--c-gray-200);
  text-decoration: none;
  font-size: 0.88rem;
  display: block;
  padding: 0.35rem 0;
  min-height: 40px;
  line-height: 40px;
  padding-top: 0;
  padding-bottom: 0;
  transition: color 0.15s;
}

.footer-col ul li a:hover { color: var(--c-white); opacity: 1; }

.footer-bar {
  border-top: 1px solid #222;
  max-width: 1400px;
  margin: 0 auto;
  padding: 1.25rem 1.5rem;
}

.footer-bar p {
  font-size: 0.8rem;
  color: var(--c-gray-500);
}

/* ===== STAGGER LIST ANIMATION ===== */
@media (prefers-reduced-motion: no-preference) {
  .card-list li {
    opacity: 0;
    transform: translateY(20px);
    animation: fadeUp 0.45s var(--ease) forwards;
  }

  .card-list li:nth-child(1) { animation-delay: 0.05s; }
  .card-list li:nth-child(2) { animation-delay: 0.12s; }
  .card-list li:nth-child(3) { animation-delay: 0.19s; }
  .card-list li:nth-child(4) { animation-delay: 0.26s; }
  .card-list li:nth-child(5) { animation-delay: 0.33s; }
  .card-list li:nth-child(6) { animation-delay: 0.40s; }

  @keyframes fadeUp {
    to { opacity: 1; transform: translateY(0); }
  }

  .sidebar ul li a {
    transition: color 0.15s, padding-left 0.2s var(--ease);
  }
}

/* ===== RESPONSIVE ===== */
@media (max-width: 960px) {
  .feature-hero {
    grid-template-columns: 1fr;
    gap: 2rem;
    padding: 4rem 1.5rem 3rem;
  }

  .content-with-aside {
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }

  .sidebar {
    position: static;
  }

  .footer-inner {
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
  }

  .footer-col:first-child {
    grid-column: 1 / -1;
  }
}

@media (max-width: 768px) {
  :root {
    --header-h: 56px;
  }

  .main-nav > p > a:not(.brand-link):not(.nav-cta) {
    display: none;
  }

  .hero-section {
    padding: 5rem 1.25rem 4rem;
    min-height: 100vh;
  }

  .inner-hero {
    padding: 4rem 1.25rem 3rem;
  }

  .about-hero {
    padding: 4.5rem 1.25rem 3.5rem;
  }

  .content-section {
    padding: 2.5rem 1.25rem 4rem;
  }

  .cards-section {
    padding: 2.5rem 1.25rem 3rem;
  }

  .cta-section {
    padding: 3rem 1.25rem 4rem;
  }

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

  .footer-inner {
    grid-template-columns: 1fr;
    gap: 1.5rem;
    padding: 3rem 1.25rem 2rem;
  }

  .footer-bar { padding: 1rem 1.25rem; }

  .sticky-subnav nav > p > a {
    padding: 0 0.75rem;
    font-size: 0.78rem;
  }

  .fullscreen-menu nav > p > a {
    font-size: clamp(1.1rem, 5vw, 1.6rem);
    padding: 0.6rem 1.5rem;
  }
}

@media (max-width: 480px) {
  .hero-h1 {
    font-size: clamp(2.5rem, 14vw, 5rem);
    letter-spacing: -0.04em;
  }

  .about-hero-text h1 {
    font-size: clamp(2rem, 12vw, 4rem);
  }

  .feature-hero-text h1 {
    font-size: clamp(1.75rem, 9vw, 3rem);
  }
}