:root {
  --color-bg: #FCFCFC;
  --color-panel: #F5F5F5;
  --color-panel-strong: #EFEFEF;
  --color-border: #E4E4E4;
  --color-accent: #111113;
  --color-accent-dark: #000000;
  --color-text: #141416;
  --color-muted: #6C6C71;
  --color-success: #1F9D62;
  --color-warn: #C4891E;
  --color-error: #D24343;
  --color-swirl-orange: #EFA45E;
  --color-swirl-pink: #EDA6C2;
  --color-swirl-teal: #82CFC3;
  --color-swirl-milk: #F6EEE5;
  --color-flag-red: #C7473F;
  --color-flag-blue: #33518F;
  --color-white: #FFFFFF;
  --color-transparent: transparent;
  --shadow-float: 0 6px 24px rgb(0 0 0 / 14%);
  --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', Menlo, Consolas, monospace;
  --radius-small: 10px;
  --radius-card: 20px;
  --radius-pill: 999px;
  --content-max: 1360px;
  --reading-max: 820px;
  --header-height: 72px;
  --gutter: clamp(16px, 3vw, 40px);
  --section-space: clamp(72px, 9vw, 128px);
  --toc-offset: 82px;
  --motion-fast: 180ms;
  --motion-slow: 560ms;
}

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

html {
  scroll-behavior: smooth;
  background: var(--color-bg);
}

html.nav-open {
  overflow: hidden;
}

body {
  margin: 0;
  min-width: 320px;
  overflow-x: clip;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  line-height: 1.65;
  -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%;
}

img {
  height: auto;
}

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

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

button {
  cursor: pointer;
}

ul,
ol {
  margin-top: 0;
}

p {
  margin: 0 0 1em;
}

h1,
h2,
h3,
h4 {
  margin: 0;
  color: var(--color-text);
  font-family: var(--font-display);
  font-weight: 400;
  line-height: 1.16;
  text-wrap: balance;
}

h1,
.hero-title {
  font-size: clamp(52px, 5vw, 72px);
  letter-spacing: -0.015em;
}

h2 {
  font-size: clamp(34px, 4vw, 52px);
  letter-spacing: -0.012em;
}

h3 {
  font-size: clamp(22px, 2.2vw, 30px);
}

strong {
  font-weight: 600;
}

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

pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 20px;
  border-radius: var(--radius-small);
  background: var(--color-panel-strong);
  -webkit-overflow-scrolling: touch;
}

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

table {
  border-collapse: collapse;
}

summary {
  cursor: pointer;
}

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

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

.reading-wrap {
  width: 100%;
  max-width: calc(var(--reading-max) + var(--gutter) * 2);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

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

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

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

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

.eyebrow,
.badge {
  display: inline-flex;
  max-width: 100%;
  align-items: center;
  gap: 8px;
  padding: 7px 14px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-pill);
  background: var(--color-bg);
  color: var(--color-muted);
  font-size: 12.5px;
  line-height: 1.25;
}

.status-dot,
.eyebrow-dot {
  width: 6px;
  height: 6px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-accent);
}

.btn {
  display: inline-flex;
  min-height: 48px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  border: 1px solid var(--color-accent);
  border-radius: var(--radius-pill);
  background: var(--color-bg);
  color: var(--color-text);
  font-size: 15px;
  font-weight: 500;
  line-height: 1.2;
  transition: color var(--motion-fast), background var(--motion-fast), transform var(--motion-fast);
}

.btn:hover {
  background: var(--color-panel);
  transform: translateY(-1px);
}

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

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

.btn-small {
  min-height: 40px;
  padding: 9px 20px;
  font-size: 13.5px;
}

.btn-disabled,
.btn:disabled {
  border-color: var(--color-border);
  background: var(--color-panel);
  color: var(--color-muted);
  cursor: not-allowed;
  transform: none;
}

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

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

.panel {
  padding: clamp(22px, 4vw, 42px);
}

.card {
  padding: 24px;
}

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

.head-in {
  position: relative;
  display: flex;
  width: 100%;
  max-width: var(--content-max);
  height: var(--header-height);
  margin-inline: auto;
  padding-inline: var(--gutter);
  align-items: center;
  gap: 28px;
}

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

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

.brand-en {
  font-size: 17px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.brand-zh {
  color: var(--color-muted);
  font-size: 14px;
  font-weight: 400;
}

.nav-tabs {
  display: flex;
  flex: 1 1 auto;
  align-items: center;
  gap: 2px;
}

.nav-tabs a {
  position: relative;
  display: block;
  padding: 25px 9px 23px;
  color: var(--color-muted);
  font-size: 13px;
  line-height: 24px;
  white-space: nowrap;
  transition: color var(--motion-fast);
}

.nav-tabs a::after {
  position: absolute;
  right: 9px;
  bottom: -1px;
  left: 9px;
  height: 2px;
  background: var(--color-accent);
  content: "";
  transform: scaleX(0);
  transform-origin: left center;
  transition: transform var(--motion-fast);
}

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

.nav-tabs a:hover::after,
.nav-tabs a.is-active::after {
  transform: scaleX(1);
}

.nav-tabs a.is-active {
  font-weight: 500;
}

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

.language-switch {
  position: relative;
}

.language-button {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 6px;
  padding: 8px 4px;
  border: 0;
  background: var(--color-transparent);
  color: var(--color-muted);
  font-size: 13px;
}

.language-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  z-index: 130;
  display: none;
  width: 172px;
  padding: 8px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-small);
  background: var(--color-bg);
}

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

.language-menu a {
  display: flex;
  min-height: 44px;
  align-items: center;
  padding: 10px 12px;
  border-radius: var(--radius-small);
  font-size: 13px;
}

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

.btn-login {
  display: inline-flex;
  min-height: 40px;
  align-items: center;
  justify-content: center;
  padding: 8px 21px;
  border: 1px solid var(--color-accent);
  border-radius: var(--radius-pill);
  font-size: 13.5px;
  font-weight: 500;
}

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

.menu-toggle {
  display: none;
  width: 44px;
  min-width: 44px;
  height: 44px;
  min-height: 44px;
  padding: 10px;
  border: 0;
  background: var(--color-transparent);
}

.menu-toggle span {
  display: block;
  width: 22px;
  height: 1px;
  margin: 5px auto;
  background: var(--color-text);
  transition: transform var(--motion-fast), opacity var(--motion-fast);
}

.menu-toggle[aria-expanded="true"] span:first-child {
  transform: translateY(6px) rotate(45deg);
}

.menu-toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}

.menu-toggle[aria-expanded="true"] span:last-child {
  transform: translateY(-6px) rotate(-45deg);
}

.mobile-drawer {
  position: absolute;
  top: var(--header-height);
  right: 0;
  left: 0;
  z-index: 125;
  display: none;
  max-height: calc(100dvh - var(--header-height));
  overflow-y: auto;
  padding: 10px var(--gutter) 22px;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
  overscroll-behavior: contain;
}

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

.mobile-drawer a {
  display: flex;
  width: 100%;
  min-height: 48px;
  align-items: center;
  padding: 12px 4px;
  border-bottom: 1px solid var(--color-border);
}

.mobile-drawer a.is-active {
  font-weight: 600;
}

.mobile-drawer .mobile-language-label {
  margin: 18px 0 4px;
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
}

.mobile-drawer .mobile-language-link {
  color: var(--color-muted);
}

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

.footer-grid {
  display: grid;
  grid-template-columns: minmax(220px, 1.3fr) repeat(3, minmax(150px, 1fr));
  gap: 44px;
  padding-top: 60px;
  padding-bottom: 48px;
}

.footer-brand p {
  max-width: 330px;
  margin-top: 18px;
  color: var(--color-muted);
  font-size: 14px;
}

.footer-title {
  margin-bottom: 16px;
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.09em;
}

.footer-links {
  display: grid;
  gap: 10px;
}

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

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

.footer-bottom {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  padding-top: 22px;
  padding-bottom: 28px;
  border-top: 1px solid var(--color-border);
  color: var(--color-muted);
  font-size: 12px;
}

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

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

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

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

.prose h2,
.prose h3 {
  margin-top: 2em;
  margin-bottom: 0.7em;
}

.prose p,
.prose li {
  color: var(--color-muted);
}

.prose a {
  text-decoration: underline;
  text-decoration-color: var(--color-border);
  text-underline-offset: 4px;
}

.prose img,
.prose table,
.prose pre {
  margin-block: 28px;
}

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

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

@media (max-width: 1180px) {
  .nav-tabs {
    display: none;
  }

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

  .menu-toggle {
    display: block;
  }
}

@media (max-width: 768px) {
  :root {
    --header-height: 64px;
  }

  h1,
  .hero-title {
    font-size: clamp(28px, 9vw, 40px);
    line-height: 1.12;
    letter-spacing: -0.01em;
  }

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

  .head-in {
    gap: 10px;
  }

  .brand-zh {
    display: none;
  }

  .language-switch {
    display: none;
  }

  .head-tools {
    margin-left: auto;
    gap: 4px;
  }

  .btn-login {
    min-height: 38px;
    padding-inline: 16px;
  }

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

  .footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .wrap,
  .reading-wrap {
    padding-inline: max(16px, var(--gutter));
  }

  .button-row {
    align-items: stretch;
  }

  .button-row .btn {
    flex: 1 1 140px;
  }

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

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .footer-brand {
    grid-column: auto;
  }

  .footer-bottom {
    flex-direction: column;
  }
}

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

  .brand-logo {
    width: 27px;
    height: 27px;
  }

  .btn-login {
    padding-inline: 13px;
  }
}

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

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

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