:root {
  --color-page: #FFFFFF;
  --color-panel: #FAFAFB;
  --color-panel-strong: #F4F4F6;
  --color-line: #E5E6E9;
  --color-ink: #16181D;
  --color-ink-deep: #0A0B0E;
  --color-muted: #6F7278;
  --color-success: #1DA750;
  --color-warning: #E08A2E;
  --color-error: #D2453E;
  --color-flag-red: #CE4340;
  --color-flag-blue: #33528F;
  --color-flag-white: #FFFFFF;
  --color-shadow-soft: rgba(10, 11, 14, 0.04);
  --color-shadow-mid: rgba(10, 11, 14, 0.06);
  --color-shadow-menu: rgba(10, 11, 14, 0.08);
  --color-shadow-button: rgba(10, 11, 14, 0.18);
  --color-success-ring: rgba(29, 167, 80, 0.12);
  --color-ambient-clear: rgba(244, 244, 246, 0);
  --font-display: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-body: "Inter", "Noto Sans SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --radius-xs: 4px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-pill: 999px;
  --shadow-window: 0 1px 2px var(--color-shadow-soft), 0 12px 32px var(--color-shadow-mid), 0 32px 72px var(--color-shadow-soft);
  --shadow-menu: 0 4px 16px var(--color-shadow-menu), 0 1px 2px var(--color-shadow-soft);
  --shadow-float: 0 8px 24px var(--color-shadow-button);
  --content-max: 1200px;
  --reading-max: 780px;
  --gutter: 32px;
  --header-height: 64px;
  --section-space: 104px;
  --toc-offset: 82px;
  --transition-fast: 160ms ease;
  --transition-reveal: 620ms cubic-bezier(0.22, 0.7, 0.3, 1);
}

*,
*::before,
*::after {
  box-sizing: border-box;
  min-width: 0;
}

html {
  background: var(--color-page);
  color: var(--color-ink);
  scroll-behavior: smooth;
  text-size-adjust: 100%;
}

html.nav-open {
  overflow: hidden;
}

body {
  margin: 0;
  min-width: 320px;
  overflow-x: clip;
  background: var(--color-page);
  color: var(--color-ink);
  font-family: var(--font-body);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

body,
button,
input,
select,
textarea {
  font: inherit;
}

img,
svg,
video,
canvas {
  display: block;
  max-width: 100%;
}

img {
  height: auto;
}

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

button,
summary {
  cursor: pointer;
}

button {
  color: inherit;
}

ul,
ol {
  margin: 0;
}

p,
h1,
h2,
h3,
h4,
figure,
blockquote {
  margin: 0;
}

table {
  border-collapse: collapse;
}

code,
kbd,
samp,
pre {
  font-family: var(--font-mono);
}

code {
  overflow-wrap: anywhere;
}

pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 18px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-panel);
  color: var(--color-ink-deep);
  -webkit-overflow-scrolling: touch;
}

::selection {
  background: var(--color-ink-deep);
  color: var(--color-page);
}

:focus-visible {
  outline: 2px solid var(--color-ink-deep);
  outline-offset: 3px;
}

.wrap {
  width: 100%;
  max-width: var(--content-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.reading {
  width: 100%;
  max-width: var(--reading-max);
  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;
}

.mono {
  font-family: var(--font-mono);
}

.nowrap-term {
  white-space: nowrap;
}

.eyebrow {
  display: block;
  margin-bottom: 12px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1,
h2,
h3,
h4 {
  color: var(--color-ink-deep);
  font-family: var(--font-display);
  text-wrap: balance;
}

h1,
.hero-title {
  font-size: clamp(52px, 5.6vw, 72px);
  font-weight: 900;
  letter-spacing: -0.02em;
  line-height: 1.1;
}

h2 {
  font-size: clamp(34px, 4vw, 52px);
  font-weight: 850;
  letter-spacing: -0.018em;
  line-height: 1.14;
}

h3 {
  font-size: clamp(22px, 2.4vw, 30px);
  font-weight: 800;
  line-height: 1.25;
}

h4 {
  font-size: 18px;
  font-weight: 750;
}

.lead {
  max-width: 760px;
  color: var(--color-muted);
  font-size: clamp(17px, 2vw, 21px);
  line-height: 1.7;
}

.muted {
  color: var(--color-muted);
}

.btn {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 11px 24px;
  border: 1px solid transparent;
  border-radius: var(--radius-pill);
  font-size: 15px;
  font-weight: 650;
  line-height: 1;
  text-align: center;
  transition: background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast), transform var(--transition-fast);
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  border-color: var(--color-ink-deep);
  background: var(--color-ink-deep);
  color: var(--color-page);
  box-shadow: 0 1px 2px var(--color-shadow-button);
}

.btn-primary:hover {
  background: var(--color-ink);
}

.btn-secondary {
  border-color: var(--color-line);
  background: var(--color-page);
  color: var(--color-ink-deep);
}

.btn-secondary:hover {
  border-color: var(--color-muted);
}

.btn-quiet {
  border-color: transparent;
  background: var(--color-panel-strong);
  color: var(--color-ink);
}

.btn[aria-disabled="true"],
.btn:disabled {
  cursor: not-allowed;
  opacity: 0.55;
  transform: none;
}

.badge,
.trust-chip,
.tag {
  display: inline-flex;
  max-width: 100%;
  align-items: center;
  gap: 8px;
  overflow: hidden;
  padding: 6px 13px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-panel);
  color: var(--color-ink);
  font-size: 12.5px;
  line-height: 1.25;
}

.badge-dot,
.status-dot,
.float-cta-dot {
  width: 7px;
  height: 7px;
  flex: 0 0 auto;
  border-radius: 50%;
  background: var(--color-success);
}

.panel,
.card {
  border: 1px solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-page);
}

.panel-soft {
  background: var(--color-panel);
}

.site-head {
  position: sticky;
  top: 0;
  z-index: 80;
  border-bottom: 1px solid var(--color-line);
  background: var(--color-page);
}

.head-bar {
  display: flex;
  height: var(--header-height);
  align-items: center;
  gap: 24px;
}

.brand {
  display: inline-flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 10px;
}

.brand-mark {
  width: 28px;
  height: 28px;
  flex: 0 0 auto;
}

.brand-copy {
  display: inline-flex;
  align-items: baseline;
  gap: 7px;
  white-space: nowrap;
}

.brand-name {
  color: var(--color-ink-deep);
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 850;
  letter-spacing: -0.01em;
}

.brand-local {
  color: var(--color-muted);
  font-size: 12px;
  font-weight: 500;
}

.desktop-nav {
  display: flex;
  align-items: center;
  gap: 4px;
}

.desktop-nav a,
.more-toggle {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  gap: 6px;
  padding: 7px 12px;
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-ink);
  font-size: 14px;
}

.desktop-nav a:hover,
.more-toggle:hover,
.desktop-nav a.is-active {
  background: var(--color-panel-strong);
}

.desktop-nav a.is-active {
  color: var(--color-ink-deep);
  font-weight: 700;
}

.nav-more {
  position: relative;
}

.more-caret {
  color: var(--color-muted);
  font-size: 10px;
}

.more-menu {
  position: absolute;
  top: 100%;
  left: 0;
  display: none;
  z-index: 90;
  padding-top: 8px;
}

.nav-more:hover .more-menu,
.nav-more:focus-within .more-menu {
  display: block;
}

.more-panel {
  min-width: 178px;
  padding: 6px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-page);
  box-shadow: var(--shadow-menu);
}

.more-panel a {
  display: flex;
  width: 100%;
  min-height: 42px;
  align-items: center;
}

.head-tools {
  display: flex;
  margin-left: auto;
  align-items: center;
  gap: 10px;
}

.language-picker {
  position: relative;
}

.language-button {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  gap: 6px;
  padding: 6px 9px;
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-muted);
  font-size: 13px;
}

.language-button:hover {
  background: var(--color-panel-strong);
  color: var(--color-ink);
}

.language-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  display: none;
  min-width: 158px;
  padding: 6px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-page);
  box-shadow: var(--shadow-menu);
}

.language-picker.is-open .language-menu {
  display: block;
}

.language-menu a {
  display: flex;
  width: 100%;
  min-height: 42px;
  align-items: center;
  padding: 8px 11px;
  border-radius: var(--radius-sm);
  font-size: 13px;
}

.language-menu a:hover,
.language-menu a[aria-current="true"] {
  background: var(--color-panel-strong);
}

.login-link {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  justify-content: center;
  padding: 7px 18px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-page);
  color: var(--color-ink-deep);
  font-size: 14px;
  font-weight: 650;
}

.login-link:hover {
  border-color: var(--color-muted);
}

.menu-button {
  display: none;
  width: 44px;
  min-width: 44px;
  height: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border: 0;
  border-radius: var(--radius-sm);
  background: var(--color-panel);
}

.menu-button svg {
  width: 20px;
  height: 20px;
}

.mobile-nav {
  position: fixed;
  top: var(--header-height);
  right: 0;
  left: 0;
  display: none;
  z-index: 95;
  max-height: calc(100dvh - var(--header-height));
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 10px var(--gutter) 24px;
  border-bottom: 1px solid var(--color-line);
  background: var(--color-page);
  box-shadow: var(--shadow-menu);
}

.mobile-nav.is-open {
  display: block;
}

.mobile-nav ul {
  padding: 0;
  list-style: none;
}

.mobile-nav a {
  display: flex;
  width: 100%;
  min-height: 46px;
  align-items: center;
  padding: 11px 10px;
  border-radius: var(--radius-sm);
  font-size: 15px;
}

.mobile-nav a:hover,
.mobile-nav a.is-active {
  background: var(--color-panel-strong);
}

.mobile-nav-label {
  display: block;
  padding: 18px 10px 5px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.nav-veil {
  position: fixed;
  inset: var(--header-height) 0 0;
  display: none;
  z-index: 70;
  border: 0;
  background: var(--color-shadow-menu);
}

.nav-veil.is-open {
  display: block;
}

.site-footer {
  border-top: 1px solid var(--color-line);
  background: var(--color-panel);
}

.footer-grid {
  display: grid;
  grid-template-columns: minmax(240px, 1.4fr) repeat(3, minmax(150px, 1fr));
  gap: 48px;
  padding-top: 72px;
  padding-bottom: 52px;
}

.footer-brand p {
  max-width: 360px;
  margin-top: 16px;
  color: var(--color-muted);
  font-size: 14px;
}

.footer-title {
  margin-bottom: 14px;
  color: var(--color-ink-deep);
  font-size: 13px;
  font-weight: 750;
}

.footer-links {
  display: grid;
  gap: 9px;
  padding: 0;
  list-style: none;
}

.footer-links a {
  color: var(--color-muted);
  font-size: 13.5px;
}

.footer-links a:hover {
  color: var(--color-ink-deep);
}

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding-top: 20px;
  padding-bottom: 28px;
  border-top: 1px solid var(--color-line);
  color: var(--color-muted);
  font-size: 12.5px;
}

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.reveal {
  transition: opacity var(--transition-reveal), transform var(--transition-reveal);
}

.reveal.pending {
  opacity: 0;
  transform: translateY(16px);
}

.reveal.shown {
  opacity: 1;
  transform: none;
}

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

.prose > * + * {
  margin-top: 20px;
}

.prose h2 {
  margin-top: 64px;
}

.prose h3 {
  margin-top: 40px;
}

.prose p,
.prose li {
  color: var(--color-ink);
  overflow-wrap: break-word;
}

.prose a {
  text-decoration: underline;
  text-underline-offset: 3px;
}

.prose ul,
.prose ol {
  padding-left: 1.4em;
}

.prose img,
.prose iframe {
  max-width: 100%;
}

body:has(.toc-tabs) section[id] {
  scroll-margin-top: var(--toc-offset);
}

.tilt,
.tilt-card {
  transform: rotate(-0.35deg);
}

@media (max-width: 960px) {
  .desktop-nav {
    display: none;
  }

  .head-tools {
    margin-left: auto;
  }

  .menu-button {
    display: inline-flex;
  }

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

@media (max-width: 768px) {
  :root {
    --gutter: 20px;
    --section-space: 76px;
  }

  h1,
  .hero-title {
    font-size: clamp(32px, 9vw, 40px);
    line-height: 1.12;
  }

  h2 {
    font-size: clamp(28px, 8vw, 38px);
  }

  .brand-local,
  .language-picker {
    display: none;
  }

  .footer-grid {
    gap: 34px;
  }

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

@media (max-width: 640px) {
  :root {
    --gutter: 16px;
  }

  .section {
    padding-top: 64px;
    padding-bottom: 64px;
  }

  .head-bar {
    gap: 8px;
  }

  .head-tools {
    gap: 7px;
  }

  .login-link {
    min-height: 36px;
    padding-inline: 14px;
  }

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

  .btn {
    white-space: normal;
  }

  .tilt,
  .tilt-card {
    transform: none;
  }

  [class*="ambient"],
  [class*="decor"],
  [class*="glow"] {
    max-width: 100%;
  }
}

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

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

  .reveal,
  .reveal.pending {
    opacity: 1;
    transform: none;
  }
}