:root {
  --color-page: #FFFFFF;
  --color-panel: #F7F7F7;
  --color-panel-strong: #EEEEEE;
  --color-line: #E2E2E2;
  --color-accent: #FA5D00;
  --color-accent-dark: #C74A00;
  --color-ink: #0B0B0B;
  --color-muted: #5F5F5F;
  --color-success: #5CA800;
  --color-warning: #E8B000;
  --color-error: #E02D63;
  --color-channel-sky: #199FE3;
  --color-channel-rose: #E02D63;
  --color-channel-orange: #FA5D00;
  --color-channel-green: #78BE00;
  --color-channel-yellow: #FFC400;
  --color-on-dark: #FFFFFF;
  --color-flag-red: #D2342A;
  --color-flag-navy: #2A3C8C;
  --color-flag-blue: #1D4FA5;
  --color-flag-gold: #F6C400;
  --color-flag-black: #161616;
  --color-flag-white: #FFFFFF;
  --color-ruler-tick: #4B4B4B;
  --color-ruler-tick-strong: #9A9A9A;
  --color-shadow-soft: rgba(11, 11, 11, 0.05);
  --color-shadow-card: rgba(11, 11, 11, 0.09);
  --color-shadow-button: rgba(11, 11, 11, 0.14);
  --color-white-ring: rgba(255, 255, 255, 0.55);
  --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', 'SFMono-Regular', Consolas, 'Liberation Mono', monospace;
  --radius-xs: 5px;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-pill: 999px;
  --shadow-card: 0 1px 2px var(--color-shadow-soft), 0 18px 44px var(--color-shadow-card);
  --shadow-button: 0 6px 16px var(--color-shadow-button);
  --wrap-width: 1160px;
  --reading-width: 56rem;
  --gutter: 32px;
  --header-height: 64px;
  --toc-offset: 76px;
  --section-space: 88px;
  --transition-fast: 150ms ease;
  --transition-reveal: 560ms cubic-bezier(0.2, 0.7, 0.3, 1);
}

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

html {
  background: var(--color-page);
  color: var(--color-ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.5;
  scroll-behavior: smooth;
  text-size-adjust: 100%;
}

html.nav-open {
  overflow: hidden;
}

body {
  margin: 0;
  min-width: 0;
  overflow-x: clip;
  background: var(--color-page);
}

body,
button,
input,
select,
textarea {
  font-family: var(--font-body);
}

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

img {
  height: auto;
}

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

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

button,
select {
  cursor: pointer;
}

button {
  border: 0;
}

p,
h1,
h2,
h3,
h4,
ul,
ol,
dl,
dd,
figure,
blockquote {
  margin: 0;
}

ul,
ol {
  padding: 0;
}

li {
  min-width: 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;
  -webkit-overflow-scrolling: touch;
}

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

::selection {
  background: var(--color-channel-yellow);
  color: var(--color-ink);
}

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

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

.section {
  padding-top: var(--section-space);
  padding-bottom: var(--section-space);
}

.section-compact {
  padding-top: 48px;
  padding-bottom: 48px;
}

.panel-section {
  background: var(--color-panel);
  border-block: 1px solid var(--color-line);
}

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

h1,
.hero-title {
  font-size: clamp(52px, 6vw, 72px);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

h2 {
  font-size: clamp(34px, 4vw, 52px);
  font-weight: 900;
  line-height: 1.12;
  letter-spacing: -0.02em;
}

h3 {
  font-size: clamp(22px, 2.5vw, 30px);
  font-weight: 800;
  line-height: 1.2;
}

h4 {
  font-size: 18px;
  font-weight: 800;
  line-height: 1.3;
}

p {
  overflow-wrap: break-word;
}

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

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  max-width: 100%;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.eyebrow::before {
  width: 7px;
  height: 7px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
  content: "";
}

.lead {
  color: var(--color-muted);
  font-size: clamp(18px, 2vw, 21px);
  line-height: 1.7;
}

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

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

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

.card,
.panel {
  min-width: 0;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-md);
  background: var(--color-page);
}

.card {
  padding: 24px;
}

.card-elevated {
  box-shadow: var(--shadow-card);
}

.badge,
.chip {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  max-width: 100%;
  min-width: 0;
  padding: 5px 12px;
  overflow: hidden;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-page);
  color: var(--color-muted);
  font-size: 13px;
  line-height: 1.25;
}

.badge-dot {
  width: 6px;
  height: 6px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-success);
}

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

.btn,
.btn-primary,
.btn-secondary,
.btn-quiet {
  display: inline-flex;
  min-height: 48px;
  align-items: center;
  justify-content: center;
  gap: 9px;
  padding: 0 28px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  font-size: 15px;
  font-weight: 700;
  line-height: 1;
  transition:
    background var(--transition-fast),
    color var(--transition-fast),
    border-color var(--transition-fast),
    transform var(--transition-fast);
}

.btn-primary {
  background: var(--color-ink);
  color: var(--color-on-dark);
  box-shadow: var(--shadow-button);
}

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

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

.btn-secondary:hover,
.btn-quiet:hover {
  background: var(--color-panel);
}

.btn-quiet {
  min-height: 40px;
  padding-inline: 18px;
  border-color: var(--color-line);
  background: var(--color-page);
  color: var(--color-ink);
}

.btn[aria-disabled="true"],
.btn:disabled {
  cursor: not-allowed;
  opacity: 0.5;
}

.btn svg,
.btn-primary svg,
.btn-secondary svg,
.btn-quiet svg {
  width: 18px;
  height: 18px;
  flex: 0 0 auto;
}

.site-mast {
  position: relative;
  z-index: 100;
  border-bottom: 1px solid var(--color-line);
  background: var(--color-page);
}

.mast-inner {
  display: flex;
  min-height: var(--header-height);
  align-items: center;
  gap: 28px;
}

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

.brand-logo {
  width: 30px;
  height: 30px;
  flex: 0 0 auto;
}

.brand-copy {
  display: flex;
  min-width: 0;
  align-items: baseline;
  gap: 7px;
}

.brand-name {
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 800;
  letter-spacing: -0.01em;
  white-space: nowrap;
}

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

.nav-tabs {
  display: flex;
  height: var(--header-height);
  align-items: stretch;
  gap: 2px;
}

.nav-tabs a {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding-inline: 9px;
  color: var(--color-muted);
  font-size: 13px;
  white-space: nowrap;
}

.nav-tabs a:hover,
.nav-tabs a.is-active {
  color: var(--color-ink);
}

.nav-tabs a.is-active {
  font-weight: 700;
}

.nav-tabs a.is-active::after {
  position: absolute;
  right: 9px;
  bottom: -1px;
  left: 9px;
  height: 2px;
  background: var(--color-ink);
  content: "";
}

.header-tools {
  display: flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 10px;
  margin-left: auto;
}

.login-link {
  display: inline-flex;
  min-height: 36px;
  align-items: center;
  justify-content: center;
  padding-inline: 17px;
  border: 1px solid var(--color-ink);
  border-radius: var(--radius-sm);
  background: var(--color-page);
  font-size: 14px;
  font-weight: 700;
}

.login-link:hover {
  background: var(--color-panel);
}

.language-menu {
  position: relative;
}

.language-trigger {
  min-height: 36px;
  padding-inline: 8px;
  background: var(--color-page);
  color: var(--color-muted);
  font-size: 13px;
}

.language-list {
  position: absolute;
  top: calc(100% + 10px);
  right: 0;
  z-index: 110;
  display: none;
  width: 176px;
  padding: 6px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-sm);
  background: var(--color-page);
  box-shadow: var(--shadow-card);
}

.language-menu.is-open .language-list {
  display: grid;
}

.language-list a {
  display: flex;
  min-height: 40px;
  align-items: center;
  padding-inline: 12px;
  border-radius: var(--radius-xs);
  font-size: 13px;
}

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

.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-sm);
  background: var(--color-page);
}

.menu-toggle-lines {
  display: grid;
  width: 18px;
  gap: 4px;
}

.menu-toggle-lines i {
  display: block;
  height: 2px;
  background: var(--color-ink);
}

.mobile-nav {
  position: absolute;
  top: 100%;
  right: 0;
  left: 0;
  z-index: 120;
  display: none;
  max-height: calc(100dvh - var(--header-height));
  overflow-y: auto;
  overscroll-behavior: contain;
  border-top: 1px solid var(--color-line);
  border-bottom: 1px solid var(--color-line);
  background: var(--color-page);
}

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

.mobile-nav-inner {
  padding-block: 10px 18px;
}

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

.mobile-nav a.is-active {
  color: var(--color-ink);
  font-weight: 800;
}

.mobile-language-label {
  padding: 18px var(--gutter) 7px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
}

.mobile-language-links {
  display: grid;
}

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

.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(220px, 1.35fr) repeat(3, minmax(150px, 1fr));
  gap: 48px;
  padding-top: 64px;
  padding-bottom: 48px;
}

.footer-brand {
  max-width: 330px;
}

.footer-brand .brand-link {
  margin-bottom: 16px;
}

.footer-brand p {
  color: var(--color-muted);
  font-size: 14px;
  line-height: 1.8;
}

.footer-title {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

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

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

.footer-links a:hover {
  color: var(--color-ink);
  text-decoration: underline;
  text-underline-offset: 4px;
}

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

.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);
  font-size: 17px;
  line-height: 1.85;
}

.prose > * + * {
  margin-top: 1.25em;
}

.prose h2 {
  margin-top: 2.1em;
}

.prose h3 {
  margin-top: 1.7em;
}

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

.prose a {
  color: var(--color-accent-dark);
  text-decoration: underline;
  text-underline-offset: 3px;
}

.prose pre {
  padding: 20px;
  border-radius: var(--radius-sm);
  background: var(--color-ink);
  color: var(--color-on-dark);
  font-size: 14px;
}

body:has(.toc-tabs) section[id] {
  scroll-margin-top: calc(var(--toc-offset) + 22px);
}

.decorative-zone,
.hero,
.hero-visual-zone {
  overflow-x: clip;
}

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

@media (max-width: 1080px) {
  .nav-tabs a {
    padding-inline: 6px;
    font-size: 12px;
  }

  .nav-tabs a.is-active::after {
    right: 6px;
    left: 6px;
  }

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

@media (max-width: 900px) {
  .nav-tabs,
  .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) {
  :root {
    --gutter: 20px;
    --section-space: 64px;
  }

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

  h2 {
    font-size: clamp(28px, 7vw, 38px);
  }

  .brand-local {
    display: none;
  }

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

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

  body,
  main,
  section,
  article,
  .wrap,
  .reading-column,
  .card,
  .panel,
  .footer-grid > *,
  [class*="grid"] > *,
  [class*="row"] > * {
    min-width: 0;
  }

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

  .mast-inner {
    gap: 8px;
  }

  .brand-copy {
    gap: 0;
  }

  .brand-name {
    font-size: 15px;
  }

  .login-link {
    min-height: 38px;
    padding-inline: 12px;
  }

  .footer-grid {
    grid-template-columns: minmax(0, 1fr);
    gap: 32px;
    padding-top: 48px;
  }

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

  .card {
    padding: 20px;
  }

  .prose {
    font-size: 16px;
  }
}

@media (max-width: 360px) {
  .brand-logo {
    width: 27px;
    height: 27px;
  }

  .login-link {
    padding-inline: 9px;
    font-size: 13px;
  }
}

@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;
  }
}