:root {
  --color-bg: #F8F8F7;
  --color-panel: #FFFFFF;
  --color-panel-alt: #EEEEEC;
  --color-border: #D9D9D5;
  --color-dot: #E2E2DF;
  --color-line: #B3B3AE;
  --color-accent: #00D9F5;
  --color-accent-ink: #0092A8;
  --color-text: #0B0B0C;
  --color-muted: #5A5B5E;
  --color-success: #12A150;
  --color-warning: #E39A00;
  --color-error: #D9322E;
  --color-flag-red: #D8262C;
  --color-flag-blue: #1E3A8A;
  --color-flag-white: #FFFFFF;
  --color-focus: #0092A8;
  --color-shadow-soft: rgba(11, 11, 12, .06);
  --color-shadow-deep: rgba(11, 11, 12, .10);
  --color-shadow-hover: rgba(11, 11, 12, .14);
  --color-accent-glow: rgba(0, 217, 245, .35);
  --font-display: 'Inter', 'Noto Sans SC', -apple-system, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --font-body: 'Inter', 'Noto Sans SC', -apple-system, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, 'Liberation Mono', monospace;
  --radius-xs: 4px;
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-round: 999px;
  --shadow-panel: 0 1px 2px var(--color-shadow-soft), 0 12px 32px var(--color-shadow-deep);
  --shadow-raised: 0 2px 4px var(--color-shadow-soft), 0 24px 56px var(--color-shadow-hover);
  --shadow-button: 0 6px 16px var(--color-accent-glow);
  --header-height: 72px;
  --content-width: 1264px;
  --reading-width: 820px;
  --gutter: 32px;
  --section-space: 104px;
  --transition-fast: 150ms ease;
  --transition-slow: 550ms cubic-bezier(.2, .7, .2, 1);
  --focus-ring: 2px solid var(--color-focus);
  --toc-offset: 112px;
}
*,
*::before,
*::after {
  box-sizing: border-box;
}
html {
  min-width: 320px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 16px);
  -webkit-text-size-adjust: 100%;
  background: var(--color-bg);
}
html.nav-open {
  overflow: hidden;
}
body {
  min-width: 320px;
  margin: 0;
  color: var(--color-text);
  background: var(--color-bg);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.65;
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}
body,
main,
section,
article,
aside,
header,
footer,
nav,
div {
  min-width: 0;
}
h1,
h2,
h3,
h4,
p,
ul,
ol,
dl,
dd,
blockquote,
figure {
  margin-top: 0;
}
h1,
h2,
h3,
h4 {
  color: var(--color-text);
  font-family: var(--font-display);
  line-height: 1.15;
  text-wrap: balance;
}
h1 {
  margin-bottom: 24px;
  font-size: clamp(52px, 5vw, 68px);
  font-weight: 900;
  letter-spacing: -.02em;
}
h2 {
  margin-bottom: 20px;
  font-size: clamp(34px, 4vw, 48px);
  font-weight: 850;
  letter-spacing: -.02em;
}
h3 {
  margin-bottom: 14px;
  font-size: clamp(22px, 2.3vw, 28px);
  font-weight: 800;
}
h4 {
  margin-bottom: 10px;
  font-size: 18px;
  font-weight: 750;
}
p {
  margin-bottom: 1em;
}
a {
  color: inherit;
  text-decoration: none;
}
img,
video,
canvas {
  display: block;
  max-width: 100%;
  height: auto;
}
svg {
  display: block;
  flex-shrink: 0;
}
button,
input,
select,
textarea {
  color: inherit;
  font: inherit;
}
button {
  cursor: pointer;
}
code,
kbd,
samp,
pre {
  font-family: var(--font-mono);
}
code {
  overflow-wrap: anywhere;
}
pre {
  max-width: 100%;
  padding: 20px;
  overflow-x: auto;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-text);
  color: var(--color-panel);
  line-height: 1.65;
  white-space: pre;
  -webkit-overflow-scrolling: touch;
}
hr {
  border: 0;
  border-top: 1px solid var(--color-border);
}
::selection {
  background: var(--color-accent);
  color: var(--color-text);
}
:where(a, button, summary, input, select, textarea, [role="tab"]):focus-visible {
  outline: var(--focus-ring);
  outline-offset: 3px;
}
.no-break {
  white-space: nowrap;
}
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  border: 0;
  white-space: nowrap;
}
.skip-link {
  position: fixed;
  top: 12px;
  left: -999px;
  z-index: 3000;
  padding: 9px 14px;
  border: 1px solid var(--color-text);
  border-radius: var(--radius-sm);
  background: var(--color-panel);
  font-weight: 700;
}
.skip-link:focus {
  left: 16px;
}
.wrap {
  width: 100%;
  max-width: var(--content-width);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.reading-wrap {
  width: 100%;
  max-width: calc(var(--reading-width) + var(--gutter) * 2);
  margin-inline: auto;
  padding-inline: var(--gutter);
}
.section {
  padding-top: var(--section-space);
  padding-bottom: var(--section-space);
}
.section-tight {
  padding-top: 64px;
  padding-bottom: 64px;
}
.section-panel {
  background: var(--color-panel);
  border-block: 1px solid var(--color-border);
}
.section-heading {
  max-width: 760px;
  margin-bottom: 44px;
}
.section-heading p {
  color: var(--color-muted);
  font-size: 18px;
}
.muted {
  color: var(--color-muted);
}
.mono {
  font-family: var(--font-mono);
}
.accent-text {
  color: var(--color-accent-ink);
}
.kicker,
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 18px;
  color: var(--color-muted);
  font-size: 12.5px;
  font-weight: 700;
  letter-spacing: .06em;
}
.kicker::before,
.eyebrow::before {
  width: 7px;
  height: 7px;
  flex-shrink: 0;
  border-radius: 50%;
  background: var(--color-text);
  content: "";
}
.section-number,
.num {
  display: inline-flex;
  width: 28px;
  height: 28px;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  border-radius: var(--radius-sm);
  background: var(--color-accent);
  color: var(--color-text);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 800;
}
.badge,
.tag,
.fact-pill {
  display: inline-flex;
  min-height: 28px;
  max-width: 100%;
  align-items: center;
  gap: 7px;
  padding: 5px 10px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-round);
  background: var(--color-panel);
  color: var(--color-text);
  font-size: 12.5px;
  font-weight: 650;
  line-height: 1.2;
  text-overflow: ellipsis;
}
.badge::before,
.fact-pill::before {
  width: 6px;
  height: 6px;
  flex-shrink: 0;
  border-radius: 2px;
  background: var(--color-text);
  content: "";
}
.badge-accent {
  border-color: var(--color-accent);
  background: var(--color-accent);
}
.tag {
  border-radius: var(--radius-sm);
  color: var(--color-accent-ink);
}
.facts {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.panel,
.card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-panel);
  box-shadow: var(--shadow-panel);
}
.panel-alt {
  background: var(--color-panel-alt);
}
.panel-dark {
  border-color: var(--color-text);
  background: var(--color-text);
  color: var(--color-panel);
}
.panel-dark h2,
.panel-dark h3,
.panel-dark h4 {
  color: var(--color-panel);
}
.btn {
  display: inline-flex;
  min-width: 24px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 13px 23px;
  border: 1.5px solid transparent;
  border-radius: var(--radius-sm);
  font-weight: 750;
  line-height: 1;
  text-align: center;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast), color var(--transition-fast);
}
.btn:hover {
  transform: translateY(-1px);
}
.btn-primary {
  border-color: var(--color-accent);
  background: var(--color-accent);
  color: var(--color-text);
}
.btn-primary:hover {
  box-shadow: var(--shadow-button);
}
.btn-secondary,
.btn-ghost {
  border-color: var(--color-text);
  background: transparent;
  color: var(--color-text);
}
.btn-secondary:hover,
.btn-ghost:hover {
  background: var(--color-panel);
}
.btn-dark {
  border-color: var(--color-text);
  background: var(--color-text);
  color: var(--color-panel);
}
.btn:disabled,
.btn.is-disabled {
  cursor: not-allowed;
  opacity: .55;
  transform: none;
  box-shadow: none;
}
.button-row,
.cta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}
.reveal {
  transition: opacity 600ms ease, transform 600ms ease;
}
.reveal.pending {
  opacity: 0;
  transform: translateY(16px);
}
.reveal.shown {
  opacity: 1;
  transform: none;
}

/* Header */
.site-header,
.top {
  position: relative;
  z-index: 1000;
  height: var(--header-height);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
}
.header-inner,
.top .wrap {
  display: flex;
  height: 100%;
  align-items: center;
  gap: 30px;
}
.site-brand,
.brand {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}
.site-brand img,
.brand img {
  width: 30px;
  height: 30px;
}
.brand-name {
  font-family: var(--font-display);
  font-size: 21px;
  font-weight: 900;
  letter-spacing: -.02em;
  line-height: 1;
}
.brand-zh {
  color: var(--color-muted);
  font-size: 13px;
  font-weight: 600;
}
.desktop-nav {
  min-width: 0;
}
.desktop-nav ul {
  display: flex;
  align-items: center;
  margin: 0;
  padding: 0;
  list-style: none;
}
.desktop-nav li {
  display: flex;
  align-items: center;
}
.desktop-nav li + li::before {
  padding-inline: 9px;
  color: var(--color-line);
  content: "·";
  font-weight: 700;
}
.desktop-nav a {
  display: inline-flex;
  min-height: 36px;
  align-items: center;
  padding: 5px 2px;
  border-bottom: 2px solid transparent;
  font-size: 14px;
  white-space: nowrap;
}
.desktop-nav a:hover {
  color: var(--color-accent-ink);
}
.desktop-nav a[aria-current="page"] {
  border-bottom-color: var(--color-text);
  font-weight: 800;
}
.header-tools {
  position: relative;
  display: flex;
  align-items: center;
  gap: 10px;
  margin-left: auto;
}
.language-control {
  position: relative;
}
.language-toggle,
.menu-toggle {
  display: inline-flex;
  min-width: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  gap: 5px;
  padding: 8px 10px;
  border: 0;
  background: transparent;
  color: var(--color-muted);
  font-size: 13px;
}
.language-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: 156px;
  padding: 6px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-panel);
  box-shadow: var(--shadow-panel);
}
.language-menu[hidden] {
  display: none;
}
.language-menu a {
  display: flex;
  min-height: 40px;
  align-items: center;
  padding: 8px 10px;
  border-radius: var(--radius-sm);
  font-size: 13px;
}
.language-menu a:hover,
.language-menu a[aria-current="true"] {
  background: var(--color-panel-alt);
  font-weight: 700;
}
.login-link,
.btn-login {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  justify-content: center;
  padding: 8px 15px;
  border: 1.5px solid var(--color-text);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 700;
  line-height: 1;
}
.login-link:hover,
.btn-login:hover {
  background: var(--color-text);
  color: var(--color-panel);
}
.menu-toggle {
  display: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
}
.menu-toggle-lines,
.menu-toggle-lines::before,
.menu-toggle-lines::after {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--color-text);
  content: "";
  transition: transform var(--transition-fast);
}
.menu-toggle-lines {
  position: relative;
}
.menu-toggle-lines::before {
  position: absolute;
  top: -6px;
}
.menu-toggle-lines::after {
  position: absolute;
  top: 6px;
}
.menu-toggle[aria-expanded="true"] .menu-toggle-lines {
  background: transparent;
}
.menu-toggle[aria-expanded="true"] .menu-toggle-lines::before {
  transform: translateY(6px) rotate(45deg);
}
.menu-toggle[aria-expanded="true"] .menu-toggle-lines::after {
  transform: translateY(-6px) rotate(-45deg);
}
.mobile-nav {
  position: absolute;
  top: var(--header-height);
  right: 0;
  left: 0;
  z-index: 1010;
  display: none;
  max-height: calc(100dvh - var(--header-height));
  padding: 10px var(--gutter) 20px;
  overflow-y: auto;
  overscroll-behavior: contain;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-panel);
  box-shadow: var(--shadow-panel);
}
.mobile-nav.is-open {
  display: block;
}
.mobile-nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}
.mobile-nav a {
  display: flex;
  width: 100%;
  min-height: 48px;
  align-items: center;
  padding: 11px 8px;
  border-bottom: 1px solid var(--color-border);
  font-weight: 650;
}
.mobile-nav a[aria-current="page"] {
  color: var(--color-accent-ink);
  font-weight: 800;
}
.mobile-language-label {
  margin: 16px 8px 5px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .08em;
  text-transform: uppercase;
}
.nav-veil {
  position: fixed;
  inset: var(--header-height) 0 0;
  z-index: 990;
  display: none;
  background: var(--color-shadow-deep);
}
.nav-veil.is-open {
  display: block;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  background: var(--color-panel);
}
.footer-main {
  display: grid;
  grid-template-columns: 1.25fr 1fr 1fr;
  gap: 54px;
  padding-top: 64px;
  padding-bottom: 50px;
}
.footer-brand p {
  max-width: 420px;
  margin-top: 18px;
  color: var(--color-muted);
}
.footer-title {
  margin-bottom: 16px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  text-transform: uppercase;
}
.footer-links {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 6px 18px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.footer-links a,
.footer-hot a,
.footer-languages a,
.footer-legal a {
  display: inline-flex;
  min-height: 30px;
  align-items: center;
  color: var(--color-muted);
}
.footer-links a:hover,
.footer-hot a:hover,
.footer-languages a:hover,
.footer-legal a:hover {
  color: var(--color-accent-ink);
}
.footer-hot {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 10px;
}
.footer-hot a {
  min-height: 32px;
  padding-inline: 8px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 12.5px;
}
.footer-bottom {
  display: flex;
  min-height: 72px;
  align-items: center;
  gap: 22px;
  padding-top: 16px;
  padding-bottom: 16px;
  border-top: 1px solid var(--color-border);
  color: var(--color-muted);
  font-size: 13px;
}
.footer-legal,
.footer-languages {
  display: flex;
  flex-wrap: wrap;
  gap: 5px 16px;
}
.footer-languages {
  margin-left: auto;
}

/* Shared prose */
.prose {
  color: var(--color-text);
  font-size: 17px;
  line-height: 1.82;
}
.prose > * {
  max-width: 100%;
}
.prose h2 {
  margin-top: 2.2em;
  scroll-margin-top: var(--toc-offset);
}
.prose h3 {
  margin-top: 1.8em;
  scroll-margin-top: var(--toc-offset);
}
.prose a:not(.btn) {
  color: var(--color-accent-ink);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}
.prose li + li {
  margin-top: .45em;
}
.prose blockquote {
  margin-inline: 0;
}
.prose img {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
}
body:has(.toc-tabs) section[id] {
  scroll-margin-top: var(--toc-offset);
}

@media (max-width: 1120px) {
  .desktop-nav li + li::before {
    padding-inline: 6px;
  }
  .desktop-nav a {
    font-size: 13px;
  }
  .header-inner {
    gap: 18px;
  }
}
@media (max-width: 960px) {
  :root {
    --gutter: 24px;
    --section-space: 82px;
  }
  .desktop-nav,
  .language-control {
    display: none;
  }
  .header-tools {
    margin-left: auto;
  }
  .menu-toggle {
    display: inline-flex;
  }
  .footer-main {
    grid-template-columns: 1fr 1fr;
  }
  .footer-brand {
    grid-column: 1 / -1;
  }
}
@media (max-width: 768px) {
  :root {
    --gutter: 20px;
    --section-space: 68px;
    --toc-offset: 104px;
  }
  h1 {
    font-size: clamp(32px, 9.2vw, 40px);
    line-height: 1.1;
  }
  h2 {
    font-size: clamp(28px, 7.5vw, 36px);
  }
  .section-heading p {
    font-size: 16px;
  }
  .footer-main {
    grid-template-columns: 1fr;
    gap: 36px;
  }
  .footer-brand {
    grid-column: auto;
  }
  .footer-bottom {
    align-items: flex-start;
    flex-direction: column;
  }
  .footer-languages {
    margin-left: 0;
  }
}
@media (max-width: 640px) {
  :root {
    --gutter: 16px;
  }
  .wrap,
  .reading-wrap {
    padding-inline: var(--gutter);
  }
  .site-header,
  .top {
    height: 64px;
  }
  :root {
    --header-height: 64px;
  }
  .brand-zh {
    display: none;
  }
  .brand-name {
    font-size: 19px;
  }
  .login-link,
  .btn-login {
    min-height: 36px;
    padding-inline: 11px;
  }
  .header-tools {
    gap: 6px;
  }
  .button-row .btn,
  .cta .btn {
    flex: 1 1 140px;
  }
  .section {
    padding-top: 60px;
    padding-bottom: 60px;
  }
  .footer-links {
    grid-template-columns: 1fr;
  }
  .tilt-card,
  [data-tilt],
  .stage,
  .mock {
    transform: none;
  }
  .hero,
  .decorated-section,
  [data-hero-visual] {
    overflow-x: clip;
  }
}
@media (max-width: 380px) {
  .site-brand img,
  .brand img {
    width: 28px;
    height: 28px;
  }
  .brand-name {
    font-size: 17px;
  }
  .login-link,
  .btn-login {
    padding-inline: 9px;
    font-size: 13px;
  }
}
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0s !important;
    animation-duration: 0s !important;
    animation-iteration-count: 1 !important;
  }
  .reveal,
  .reveal.pending,
  .reveal.shown {
    opacity: 1;
    transform: none;
  }
}