:root {
  --color-bg: #F6F5F1;
  --color-panel: #FFFFFF;
  --color-panel-secondary: #E9ECE8;
  --color-border: #D8DAD5;
  --color-accent: #0B9B78;
  --color-accent-dark: #076A55;
  --color-text: #17201F;
  --color-text-muted: #626B68;
  --color-success: #24775F;
  --color-warning: #8A6A2F;
  --color-error: #9A4E4B;
  --color-device: #092C2A;
  --color-device-deep: #061F1E;
  --color-device-mid: #12423E;
  --color-device-line: #28514D;
  --color-device-text: #DCEBE7;
  --color-device-muted: #91AAA5;
  --color-scene-sky: #89BFB4;
  --color-scene-water: #247F72;
  --color-scene-light: #BDE4D5;
  --color-scene-dark: #174E49;
  --color-scene-shadow: #103A37;
  --color-scene-sun: #DCECE3;
  --color-flag-red: #B84F51;
  --color-flag-blue: #315B85;
  --color-flag-yellow: #D3B253;
  --color-flag-white: #FFFFFF;
  --color-flag-black: #17201F;
  --color-transparent: transparent;
  --color-grid-line: rgba(23, 32, 31, 0.045);
  --color-shadow-soft: rgba(23, 32, 31, 0.08);
  --color-shadow-medium: rgba(23, 32, 31, 0.13);
  --color-shadow-device: rgba(6, 31, 30, 0.18);
  --color-white-halo: rgba(255, 255, 255, 0.78);
  --color-device-glass: rgba(255, 255, 255, 0.06);
  --color-device-seam: rgba(255, 255, 255, 0.24);
  --color-accent-soft: rgba(11, 155, 120, 0.12);
  --color-accent-line: rgba(11, 155, 120, 0.38);
  --font-display: Inter, "Noto Sans SC", "Noto Sans JP", "Noto Sans KR", system-ui, sans-serif;
  --font-body: Inter, "Noto Sans SC", "Noto Sans JP", "Noto Sans KR", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Consolas, monospace;
  --radius-xs: 4px;
  --radius-sm: 7px;
  --radius-md: 10px;
  --radius-pill: 999px;
  --shadow-header: 0 1px 0 var(--color-border);
  --shadow-button: 0 5px 14px var(--color-shadow-soft);
  --shadow-panel: 0 12px 32px var(--color-shadow-soft);
  --shadow-device: 0 22px 48px var(--color-shadow-device);
  --wrap-max: 1200px;
  --reading-max: 768px;
  --header-height: 72px;
  --toc-top: 12px;
  --toc-offset: 84px;
  --gutter: clamp(16px, 4vw, 32px);
  --section-space: clamp(72px, 9vw, 128px);
  --transition-fast: 160ms ease;
  --transition-slow: 520ms cubic-bezier(0.22, 1, 0.36, 1);
}

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

html {
  min-width: 320px;
  scroll-behavior: smooth;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  text-rendering: optimizeLegibility;
}

html.nav-open {
  overflow: hidden;
}

body {
  min-width: 320px;
  min-height: 100vh;
  margin: 0;
  overflow-x: clip;
  background: var(--color-bg);
  color: var(--color-text);
  font-size: 16px;
  line-height: 1.7;
}

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 {
  font: inherit;
}

button,
a,
summary {
  -webkit-tap-highlight-color: var(--color-transparent);
}

button {
  border: 0;
}

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

p {
  margin-bottom: 1.2em;
}

ul,
ol {
  padding-left: 1.3em;
}

li + li {
  margin-top: 0.45em;
}

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

:not(pre) > code {
  padding: 0.12em 0.35em;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xs);
  background: var(--color-panel-secondary);
  font-size: 0.9em;
  overflow-wrap: anywhere;
  word-break: break-word;
}

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

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

hr {
  margin: 48px 0;
  border: 0;
  border-top: 1px solid var(--color-border);
}

::selection {
  background: var(--color-accent-soft);
  color: var(--color-text);
}

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

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

h1,
.hero-title {
  font-size: clamp(52px, 5.2vw, 72px);
  font-weight: 430;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

h2 {
  margin-bottom: 22px;
  font-size: clamp(34px, 4vw, 52px);
  font-weight: 440;
  line-height: 1.16;
  letter-spacing: -0.018em;
}

h3 {
  margin-bottom: 14px;
  font-size: clamp(22px, 2.5vw, 30px);
  font-weight: 520;
  line-height: 1.3;
}

h4 {
  margin-bottom: 10px;
  font-size: 18px;
  font-weight: 600;
}

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

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

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

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

.wrap {
  width: 100%;
  max-width: calc(var(--wrap-max) + var(--gutter) * 2);
  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;
}

.section-compact {
  padding-top: calc(var(--section-space) * 0.62);
  padding-bottom: calc(var(--section-space) * 0.62);
  overflow-x: clip;
}

.section-heading {
  max-width: 760px;
  margin-bottom: 42px;
}

.section-heading.centered {
  margin-inline: auto;
  text-align: center;
}

.kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  max-width: 100%;
  min-height: 28px;
  padding: 0 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-pill);
  background: var(--color-panel);
  color: var(--color-text-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  box-shadow: 0 4px 12px var(--color-shadow-soft);
}

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

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  max-width: 100%;
  min-height: 27px;
  padding: 0 10px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-pill);
  background: var(--color-panel);
  color: var(--color-text-muted);
  font-size: 12px;
  line-height: 1.35;
}

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

.button,
.cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-width: 128px;
  min-height: 44px;
  padding: 0 20px;
  border: 1px solid var(--color-transparent);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 15px;
  font-weight: 600;
  line-height: 1.2;
  text-align: center;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast);
}

.button:hover,
.cta:hover {
  transform: translateY(-1px);
}

.button-primary,
.cta-primary {
  border-color: var(--color-accent);
  background: var(--color-accent);
  color: var(--color-panel);
  box-shadow: var(--shadow-button);
}

.button-primary:hover,
.cta-primary:hover {
  border-color: var(--color-accent-dark);
  background: var(--color-accent-dark);
}

.button-secondary,
.cta-secondary {
  border-color: var(--color-border);
  background: var(--color-panel);
  color: var(--color-text);
}

.button-secondary:hover,
.cta-secondary:hover {
  border-color: var(--color-accent-line);
}

.button-ghost {
  background: var(--color-transparent);
  color: var(--color-accent-dark);
}

.button:disabled,
.button.is-disabled {
  cursor: not-allowed;
  opacity: 0.5;
  transform: none;
}

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

.panel {
  padding: clamp(22px, 4vw, 40px);
}

.card {
  padding: 24px;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), border-color var(--transition-fast);
}

.card:hover {
  border-color: var(--color-accent-line);
  box-shadow: var(--shadow-panel);
}

.panel-dark {
  border-color: var(--color-device-line);
  background: var(--color-device);
  color: var(--color-device-text);
}

.panel-dark h2,
.panel-dark h3,
.panel-dark h4 {
  color: var(--color-device-text);
}

.panel-dark p {
  color: var(--color-device-muted);
}

.site-header {
  position: relative;
  z-index: 100;
  min-height: var(--header-height);
  background: var(--color-bg);
  box-shadow: var(--shadow-header);
}

.header-inner {
  width: min(1320px, calc(100% - 48px));
  min-height: var(--header-height);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 22px;
}

.brand {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  min-width: 190px;
}

.brand-logo,
.brand-mark {
  width: 25px;
  height: 29px;
  flex: 0 0 25px;
  object-fit: contain;
}

.brand-en {
  font-family: var(--font-display);
  font-size: 19px;
  font-weight: 650;
  letter-spacing: 0.045em;
}

.brand-zh {
  padding-left: 9px;
  border-left: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-size: 13px;
  font-weight: 450;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.primary-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  margin-left: auto;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 9px 11px;
  border-radius: var(--radius-pill);
  color: var(--color-text-muted);
  font-size: 14px;
  line-height: 1;
  white-space: nowrap;
  transition: color var(--transition-fast), background-color var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-text);
  background: var(--color-panel-secondary);
}

.nav-link[aria-current="page"] {
  color: var(--color-text);
  background: var(--color-panel);
  box-shadow: inset 0 0 0 1px var(--color-border);
}

.header-tools {
  position: relative;
  display: flex;
  align-items: center;
  gap: 8px;
  margin-left: 8px;
}

.language-control {
  position: relative;
}

.language-button {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 38px;
  padding: 0 8px;
  border-radius: var(--radius-sm);
  background: var(--color-transparent);
  color: var(--color-text-muted);
  cursor: pointer;
  font-size: 13px;
}

.language-button svg {
  width: 14px;
  height: 14px;
}

.language-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: 158px;
  padding: 6px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-panel);
  box-shadow: var(--shadow-panel);
}

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

.language-menu a {
  display: flex;
  align-items: center;
  min-height: 40px;
  padding: 0 10px;
  border-radius: var(--radius-xs);
  color: var(--color-text-muted);
  font-size: 13px;
}

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

.login-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 0 17px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-panel);
  color: var(--color-text);
  font-size: 14px;
  font-weight: 550;
  white-space: nowrap;
}

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

.menu-toggle svg {
  width: 22px;
  height: 22px;
}

.mobile-nav {
  display: none;
}

.mobile-nav-veil {
  display: none;
}

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

.footer-main {
  display: grid;
  grid-template-columns: minmax(220px, 1.25fr) repeat(3, minmax(150px, 1fr));
  gap: clamp(28px, 5vw, 72px);
  padding-top: 64px;
  padding-bottom: 56px;
}

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

.footer-brand-line {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 18px;
}

.footer-brand-line img {
  width: 28px;
  height: 32px;
}

.footer-brand-line strong {
  font-family: var(--font-display);
  font-size: 20px;
  letter-spacing: 0.04em;
}

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

.footer-column h2 {
  margin-bottom: 16px;
  font-size: 13px;
  font-weight: 650;
  letter-spacing: 0.08em;
}

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

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

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

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding-top: 20px;
  padding-bottom: 24px;
  border-top: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-size: 12px;
}

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

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

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

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

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

.prose h2,
.prose h3 {
  scroll-margin-top: var(--toc-offset);
}

.prose h2 {
  margin-top: 2.2em;
}

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

.prose blockquote {
  margin: 28px 0;
  padding: 18px 22px;
  border-left: 3px solid var(--color-accent);
  background: var(--color-panel-secondary);
  color: var(--color-text-muted);
}

.prose img {
  margin: 32px auto;
  border-radius: var(--radius-sm);
}

.prose > table {
  width: 100%;
}

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

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

@media (max-width: 1180px) {
  .header-inner {
    width: min(1060px, calc(100% - 32px));
    gap: 12px;
  }

  .brand {
    min-width: 150px;
  }

  .brand-zh {
    display: none;
  }

  .nav-link {
    padding-inline: 8px;
    font-size: 13px;
  }

  .language-button span {
    display: none;
  }
}

@media (max-width: 900px) {
  :root {
    --header-height: 64px;
    --toc-offset: 76px;
  }

  .header-inner {
    width: 100%;
    padding-inline: var(--gutter);
  }

  .primary-nav,
  .desktop-language {
    display: none;
  }

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

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

  .mobile-nav-veil {
    position: fixed;
    z-index: 98;
    inset: var(--header-height) 0 0;
    background: var(--color-shadow-medium);
  }

  .site-header.menu-open .mobile-nav-veil {
    display: block;
  }

  .mobile-nav {
    position: fixed;
    z-index: 101;
    top: var(--header-height);
    left: 0;
    right: 0;
    max-height: calc(100dvh - var(--header-height));
    padding: 10px var(--gutter) 20px;
    overflow-y: auto;
    overscroll-behavior: contain;
    border-top: 1px solid var(--color-border);
    background: var(--color-panel);
    box-shadow: var(--shadow-panel);
  }

  .site-header.menu-open .mobile-nav {
    display: block;
  }

  .mobile-nav a {
    display: flex;
    align-items: center;
    width: 100%;
    min-height: 48px;
    padding: 11px 12px;
    border-bottom: 1px solid var(--color-border);
    color: var(--color-text);
  }

  .mobile-nav a[aria-current="page"] {
    background: var(--color-panel-secondary);
    color: var(--color-accent-dark);
  }

  .mobile-language-list {
    margin-top: 12px;
    padding-top: 6px;
  }

  .mobile-language-list strong {
    display: block;
    padding: 8px 12px;
    color: var(--color-text-muted);
    font-size: 12px;
  }

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

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

@media (max-width: 768px) {
  h1,
  .hero-title {
    font-size: clamp(28px, 9vw, 40px);
    line-height: 1.14;
  }

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

  .section-heading {
    margin-bottom: 30px;
  }

  .decorative-label,
  .decorative-copy {
    display: none;
  }
}

@media (max-width: 640px) {
  :root {
    --gutter: 16px;
    --section-space: 68px;
  }

  body {
    overflow-x: clip;
  }

  .header-inner {
    padding-inline: var(--gutter);
  }

  .brand {
    min-width: 0;
  }

  .brand-en {
    font-size: 17px;
  }

  .brand-zh {
    display: none;
  }

  .login-button {
    min-height: 40px;
    padding-inline: 12px;
  }

  .wrap,
  .reading-wrap {
    width: 100%;
    padding-inline: var(--gutter);
  }

  .button,
  .cta {
    max-width: 100%;
  }

  .panel,
  .card {
    padding: 20px;
  }

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

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

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

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

@media (max-width: 420px) {
  .brand-logo,
  .brand-mark {
    width: 22px;
    height: 26px;
  }

  .header-tools {
    gap: 5px;
  }

  .login-button {
    padding-inline: 10px;
    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;
  }
}