:root {
  --color-canvas: #FFFFFF;
  --color-panel: #FAFBFD;
  --color-panel-strong: #F2F5F9;
  --color-line: #E3E7EE;
  --color-accent: #1E4FDB;
  --color-accent-deep: #1638A8;
  --color-ink: #0E1526;
  --color-muted: #5B6577;
  --color-success: #1A9A5B;
  --color-warning: #C08A1F;
  --color-error: #D6483C;
  --color-overlay: rgba(14, 21, 38, 0.44);
  --color-shadow-soft: rgba(14, 21, 38, 0.05);
  --color-shadow: rgba(14, 21, 38, 0.08);
  --color-accent-shadow: rgba(30, 79, 219, 0.20);
  --font-display: 'Inter', 'Noto Sans SC', -apple-system, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-body: 'Inter', 'Noto Sans SC', -apple-system, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Consolas, monospace;
  --radius-small: 8px;
  --radius-medium: 10px;
  --radius-large: 14px;
  --radius-pill: 999px;
  --shadow-panel: 0 1px 2px var(--color-shadow-soft), 0 8px 24px var(--color-shadow-soft);
  --shadow-button: 0 2px 4px var(--color-accent-shadow), 0 10px 26px var(--color-accent-shadow);
  --shadow-button-hover: 0 4px 8px var(--color-accent-shadow), 0 14px 30px var(--color-accent-shadow);
  --content-width: 1200px;
  --reading-width: 768px;
  --header-height: 64px;
  --gutter: clamp(16px, 4vw, 32px);
  --section-space: clamp(72px, 10vw, 128px);
  --toc-offset: 76px;
  --motion-fast: 150ms;
  --motion-base: 420ms;
}

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

html {
  margin: 0;
  padding: 0;
  scroll-behavior: smooth;
  overflow-x: clip;
}

html.nav-open {
  overflow: hidden;
}

body {
  min-width: 320px;
  margin: 0;
  padding: 0;
  overflow-x: clip;
  background: var(--color-canvas);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

main,
section,
article,
aside,
header,
footer,
nav,
div {
  min-width: 0;
}

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

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

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

button {
  border: 0;
}

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

p,
ul,
ol,
blockquote,
pre,
table {
  margin-top: 0;
}

p {
  margin-bottom: 1.2em;
}

ul,
ol {
  padding-left: 1.35em;
}

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

:not(pre) > code {
  overflow-wrap: anywhere;
  padding: 0.12em 0.38em;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-small);
  background: var(--color-panel-strong);
  font-size: 0.88em;
}

pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 20px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-medium);
  background: var(--color-ink);
  color: var(--color-canvas);
  line-height: 1.65;
  -webkit-overflow-scrolling: touch;
}

pre code {
  white-space: pre;
  overflow-wrap: normal;
}

table {
  border-collapse: collapse;
}

th,
td {
  padding: 13px 16px;
  border-bottom: 1px solid var(--color-line);
  text-align: left;
  vertical-align: top;
}

th {
  color: var(--color-ink);
  font-size: 13px;
  font-weight: 750;
}

h1,
h2,
h3,
h4 {
  margin-top: 0;
  color: var(--color-ink);
  font-family: var(--font-display);
  text-wrap: balance;
}

h1 {
  max-width: 100%;
  margin-bottom: 24px;
  font-size: clamp(52px, 6vw, 72px);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.1;
}

h2 {
  margin-bottom: 20px;
  font-size: clamp(34px, 4vw, 52px);
  font-weight: 800;
  letter-spacing: -0.018em;
  line-height: 1.16;
}

h3 {
  margin-bottom: 12px;
  font-size: clamp(22px, 2.4vw, 30px);
  font-weight: 760;
  line-height: 1.28;
}

h4 {
  margin-bottom: 10px;
  font-size: 18px;
  font-weight: 750;
  line-height: 1.4;
}

.word-lock {
  white-space: nowrap;
}

.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-compact {
  padding-top: clamp(48px, 7vw, 80px);
  padding-bottom: clamp(48px, 7vw, 80px);
}

.panel {
  border: 1px solid var(--color-line);
  border-radius: var(--radius-medium);
  background: var(--color-canvas);
  box-shadow: var(--shadow-panel);
}

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

.eyebrow {
  display: inline-flex;
  max-width: 100%;
  align-items: center;
  gap: 9px;
  padding: 6px 16px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-panel);
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  line-height: 1.4;
}

.eyebrow-dot,
.status-dot {
  width: 7px;
  height: 7px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
}

.status-dot {
  background: var(--color-success);
}

.lead {
  max-width: 760px;
  color: var(--color-muted);
  font-size: clamp(18px, 2vw, 21px);
  line-height: 1.75;
}

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

.accent-text {
  color: var(--color-accent);
}

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

.badge,
.chip,
.tag {
  display: inline-flex;
  max-width: 100%;
  align-items: center;
  gap: 7px;
  overflow: hidden;
  padding: 5px 13px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-panel);
  color: var(--color-muted);
  font-size: 13px;
  line-height: 1.4;
  text-overflow: ellipsis;
}

.badge-accent {
  border-color: var(--color-accent);
  background: var(--color-accent);
  color: var(--color-canvas);
}

.badge-success {
  color: var(--color-success);
}

.icon,
.chip svg,
.badge svg,
.button svg {
  flex: 0 0 auto;
}

.button,
.btn-primary,
.btn-secondary,
.btn-login {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border-radius: var(--radius-medium);
  font-weight: 750;
  line-height: 1.2;
  cursor: pointer;
  transition: transform var(--motion-fast) ease, background var(--motion-fast) ease, border-color var(--motion-fast) ease, box-shadow var(--motion-fast) ease;
}

.btn-primary {
  padding: 15px 34px;
  background: var(--color-accent);
  color: var(--color-canvas);
  box-shadow: var(--shadow-button);
}

.btn-primary:hover,
.btn-primary:focus-visible {
  transform: translateY(-1px);
  background: var(--color-accent-deep);
  box-shadow: var(--shadow-button-hover);
}

.btn-secondary {
  padding: 14px 28px;
  border: 1px solid var(--color-line);
  background: var(--color-canvas);
  color: var(--color-ink);
  box-shadow: var(--shadow-panel);
}

.btn-secondary:hover,
.btn-secondary:focus-visible {
  transform: translateY(-1px);
  border-color: var(--color-muted);
}

.btn-login {
  min-height: 38px;
  padding: 8px 20px;
  background: var(--color-accent);
  color: var(--color-canvas);
  font-size: 14px;
}

.btn-login:hover,
.btn-login:focus-visible {
  background: var(--color-accent-deep);
}

.button:disabled,
.btn-primary:disabled,
.btn-secondary:disabled {
  opacity: 0.55;
  cursor: not-allowed;
  transform: none;
}

:focus-visible {
  outline: 3px solid var(--color-accent-shadow);
  outline-offset: 3px;
}

.cta-row {
  display: flex;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}

.site-header {
  position: relative;
  z-index: 100;
  min-height: var(--header-height);
  border-bottom: 1px solid var(--color-line);
  background: var(--color-canvas);
}

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

.brand {
  display: inline-flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 10px;
  color: var(--color-ink);
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.brand img {
  width: 28px;
  height: 28px;
}

.brand-local {
  color: var(--color-muted);
  font-weight: 600;
}

.desktop-nav {
  display: flex;
  align-items: center;
  gap: 24px;
  margin-left: auto;
}

.desktop-nav a {
  position: relative;
  padding-block: 20px;
  color: var(--color-muted);
  font-size: 14px;
  font-weight: 550;
  white-space: nowrap;
}

.desktop-nav a:hover,
.desktop-nav a.active,
.desktop-nav a[aria-current="page"] {
  color: var(--color-ink);
}

.desktop-nav a.active,
.desktop-nav a[aria-current="page"] {
  font-weight: 750;
}

.header-tools {
  display: flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 12px;
}

.language-menu {
  position: relative;
}

.language-button {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 6px;
  padding: 6px 8px;
  background: transparent;
  color: var(--color-muted);
  cursor: pointer;
  font-size: 13px;
}

.language-popover {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  z-index: 130;
  width: 154px;
  padding: 6px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-medium);
  background: var(--color-canvas);
  box-shadow: var(--shadow-panel);
}

.language-popover[hidden] {
  display: none;
}

.language-popover a {
  display: block;
  min-height: 42px;
  padding: 9px 10px;
  border-radius: var(--radius-small);
  color: var(--color-muted);
  font-size: 13px;
}

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

.menu-toggle {
  display: none;
  min-width: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-small);
  background: var(--color-canvas);
  color: var(--color-ink);
  cursor: pointer;
}

.menu-toggle-lines,
.menu-toggle-lines::before,
.menu-toggle-lines::after {
  display: block;
  width: 18px;
  height: 2px;
  border-radius: var(--radius-pill);
  background: var(--color-ink);
}

.menu-toggle-lines {
  position: relative;
}

.menu-toggle-lines::before,
.menu-toggle-lines::after {
  position: absolute;
  left: 0;
  content: "";
}

.menu-toggle-lines::before {
  top: -6px;
}

.menu-toggle-lines::after {
  top: 6px;
}

.mobile-nav {
  display: none;
  position: absolute;
  top: var(--header-height);
  right: 0;
  left: 0;
  z-index: 125;
  max-height: calc(100dvh - var(--header-height));
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 10px var(--gutter) 18px;
  border-top: 1px solid var(--color-line);
  border-bottom: 1px solid var(--color-line);
  background: var(--color-canvas);
  box-shadow: var(--shadow-panel);
}

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

.mobile-nav a {
  display: flex;
  width: 100%;
  min-height: 46px;
  align-items: center;
  padding: 11px 8px;
  border-bottom: 1px solid var(--color-line);
  color: var(--color-muted);
}

.mobile-nav a.active,
.mobile-nav a[aria-current="page"] {
  color: var(--color-ink);
  font-weight: 750;
}

.mobile-nav-languages {
  padding-top: 10px;
}

.mobile-nav-languages strong {
  display: block;
  padding: 8px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
}

.mobile-nav-languages a {
  min-height: 44px;
}

.menu-veil {
  display: none;
  position: fixed;
  inset: var(--header-height) 0 0;
  z-index: 90;
  background: var(--color-overlay);
}

.menu-veil.open {
  display: block;
}

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

.footer-grid {
  display: grid;
  grid-template-columns: minmax(240px, 1.2fr) repeat(3, minmax(150px, 1fr));
  gap: 48px;
  padding-top: 64px;
  padding-bottom: 48px;
}

.footer-brand p {
  max-width: 340px;
  margin-top: 18px;
  color: var(--color-muted);
  font-size: 14px;
}

.footer-title {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
}

.footer-links {
  display: grid;
  gap: 9px;
}

.footer-links a {
  color: var(--color-muted);
  font-size: 14px;
}

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

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding-top: 22px;
  padding-bottom: 28px;
  border-top: 1px solid var(--color-line);
  color: var(--color-muted);
  font-size: 13px;
}

.footer-legal {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}

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

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

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

.tilt {
  transform: rotate(-0.45deg);
}

body:has(.toc-tabs) section[id] {
  scroll-margin-top: calc(var(--toc-offset) + 28px);
}

@media (max-width: 1100px) {
  .desktop-nav {
    gap: 15px;
  }

  .desktop-nav a {
    font-size: 13px;
  }
}

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

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

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

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

@media (max-width: 768px) {
  h1 {
    font-size: clamp(28px, 9.6vw, 40px);
    line-height: 1.14;
  }

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

  .header-inner {
    gap: 10px;
  }

  .brand-local {
    display: none;
  }

  .btn-login {
    min-height: 40px;
    padding-inline: 15px;
  }

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

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

  .wrap,
  .reading-wrap {
    padding-inline: var(--gutter);
  }

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

  .section-compact {
    padding-top: 44px;
    padding-bottom: 44px;
  }

  .cta-row {
    width: 100%;
  }

  .cta-row .btn-primary,
  .cta-row .btn-secondary {
    width: 100%;
  }

  .tilt,
  [class*="tilt"] {
    transform: none;
  }

  .footer-grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
  }
}

@media (max-width: 390px) {
  .brand {
    gap: 7px;
    font-size: 15px;
  }

  .brand img {
    width: 25px;
    height: 25px;
  }

  .header-tools {
    gap: 7px;
  }

  .btn-login {
    padding-inline: 12px;
  }
}

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

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

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