:root {
  --color-canvas: #FDFDFC;
  --color-surface: #F6F7F8;
  --color-surface-strong: #EFF1F3;
  --color-line: #E2E5E8;
  --color-accent: #0B5BD7;
  --color-accent-deep: #083F9A;
  --color-ink: #17191D;
  --color-ink-soft: #5B6168;
  --color-success: #0C8A5F;
  --color-warning: #C77E12;
  --color-error: #C2372E;
  --color-encode-teal: #0FB5A6;
  --color-encode-amber: #F2A33C;
  --color-white: #FFFFFF;
  --color-code-white: rgba(255, 255, 255, 0.85);
  --color-hair-white: rgba(255, 255, 255, 0.38);
  --color-shadow: rgba(23, 25, 29, 0.16);
  --color-shadow-soft: rgba(23, 25, 29, 0.08);
  --color-accent-tint: rgba(11, 91, 215, 0.08);
  --color-success-tint: rgba(12, 138, 95, 0.09);
  --color-warning-tint: rgba(199, 126, 18, 0.1);
  --color-error-tint: rgba(194, 55, 46, 0.09);
  --color-flag-red: #C4302B;
  --color-flag-blue: #2A4E8F;
  --color-flag-gold: #F5C400;
  --font-display: Georgia, "Times New Roman", "Songti SC", "Noto Serif CJK SC", "Hiragino Mincho ProN", serif;
  --font-body: "Inter", "Noto Sans SC", "Noto Sans JP", "Noto Sans KR", -apple-system, "PingFang SC", "Hiragino Sans", sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Courier New", monospace;
  --radius-small: 6px;
  --radius-medium: 12px;
  --radius-large: 18px;
  --radius-panel: 26px;
  --radius-pill: 999px;
  --layout-max: 1400px;
  --reading-max: 900px;
  --gutter: 40px;
  --header-height: 64px;
  --toc-offset: 76px;
  --space-section: clamp(72px, 9vw, 132px);
  --duration-fast: 150ms;
  --duration-reveal: 560ms;
  --ease-standard: cubic-bezier(0.22, 1, 0.36, 1);
}

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

html {
  margin: 0;
  padding: 0;
  scroll-behavior: smooth;
  background: var(--color-canvas);
}

html.nav-open {
  overflow: hidden;
}

body {
  min-width: 0;
  margin: 0;
  padding: 0;
  overflow-x: clip;
  background: var(--color-canvas);
  color: var(--color-ink);
  font-family: var(--font-body);
  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,
canvas {
  display: block;
  max-width: 100%;
}

img {
  height: auto;
}

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

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

button {
  cursor: pointer;
}

a {
  color: var(--color-accent);
  text-underline-offset: 0.18em;
  transition:
    color var(--duration-fast) ease,
    opacity var(--duration-fast) ease,
    border-color var(--duration-fast) ease,
    background-color var(--duration-fast) ease,
    transform var(--duration-fast) ease;
}

a:hover {
  color: var(--color-accent-deep);
}

a:focus-visible,
button:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

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

p {
  margin-bottom: 1.1em;
}

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

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

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

h1,
.display-title {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(52px, 5vw, 72px);
  font-weight: 400;
  letter-spacing: 0.01em;
  line-height: 1.12;
}

h2 {
  margin: 0 0 0.55em;
  font-family: var(--font-display);
  font-size: clamp(36px, 4vw, 56px);
  font-weight: 400;
  letter-spacing: 0.01em;
  line-height: 1.16;
}

h3 {
  margin: 0 0 0.55em;
  font-size: clamp(21px, 2vw, 28px);
  font-weight: 650;
  line-height: 1.3;
}

h4 {
  margin: 0 0 0.5em;
  font-size: 18px;
  font-weight: 650;
}

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

small,
.text-small {
  font-size: 0.875rem;
}

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

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

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

code {
  overflow-wrap: anywhere;
}

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

pre code {
  overflow-wrap: normal;
}

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

.wrap {
  width: 100%;
  max-width: var(--layout-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(--space-section);
  padding-bottom: var(--space-section);
}

.section-tight {
  padding-top: clamp(48px, 6vw, 80px);
  padding-bottom: clamp(48px, 6vw, 80px);
}

.section-head {
  max-width: 850px;
  margin-bottom: clamp(36px, 5vw, 64px);
}

.section-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  color: var(--color-accent);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.13em;
  text-transform: uppercase;
}

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

.lead {
  max-width: 42em;
  color: var(--color-ink-soft);
  font-size: clamp(17px, 1.6vw, 21px);
  line-height: 1.8;
}

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

.surface-soft {
  border: 1px solid var(--color-line);
  border-radius: var(--radius-medium);
  background: var(--color-surface);
}

.panel {
  padding: clamp(24px, 4vw, 48px);
  border: 1px solid var(--color-line);
  border-radius: var(--radius-large);
  background: var(--color-canvas);
}

.badge,
.tag {
  display: inline-flex;
  max-width: 100%;
  min-width: 0;
  align-items: center;
  gap: 8px;
  overflow: hidden;
  padding: 6px 13px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-pill);
  background: var(--color-surface);
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  line-height: 1.35;
}

.badge-dot {
  width: 7px;
  height: 7px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-success);
}

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

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

.button,
.btn-main,
.btn-sub,
.btn-small {
  display: inline-flex;
  min-height: 48px;
  align-items: center;
  justify-content: center;
  gap: 9px;
  border: 1px solid transparent;
  border-radius: var(--radius-small);
  font-weight: 650;
  line-height: 1.2;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
}

.button,
.btn-main {
  padding: 14px 32px;
  background: var(--color-ink);
  color: var(--color-canvas);
}

.button:hover,
.btn-main:hover {
  color: var(--color-canvas);
  opacity: 0.86;
}

.button-accent {
  background: var(--color-accent);
  color: var(--color-white);
}

.button-accent:hover {
  background: var(--color-accent-deep);
  color: var(--color-white);
  opacity: 1;
}

.btn-sub,
.button-outline {
  padding: 13px 30px;
  border-color: var(--color-ink);
  background: transparent;
  color: var(--color-ink);
}

.btn-sub:hover,
.button-outline:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.button-quiet {
  border-color: var(--color-line);
  background: var(--color-surface);
  color: var(--color-ink);
}

.button-quiet:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn-small {
  min-height: 40px;
  padding: 10px 18px;
  background: var(--color-ink);
  color: var(--color-canvas);
  font-size: 13px;
}

.button[disabled],
.button.is-disabled {
  border-color: var(--color-line);
  background: var(--color-surface-strong);
  color: var(--color-ink-soft);
  cursor: not-allowed;
  opacity: 0.65;
}

.button svg,
.btn-main svg,
.btn-sub svg,
.btn-small svg {
  width: 18px;
  height: 18px;
  flex: 0 0 auto;
}

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

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

.site-header-inner {
  display: flex;
  height: var(--header-height);
  align-items: center;
  gap: 38px;
}

.site-brand {
  display: inline-flex;
  flex: 0 0 auto;
  align-items: center;
  gap: 10px;
  color: var(--color-ink);
  text-decoration: none;
}

.site-brand:hover {
  color: var(--color-ink);
}

.site-brand img {
  width: 27px;
  height: 27px;
}

.brand-word {
  font-size: 18px;
  font-weight: 750;
  letter-spacing: 0.02em;
}

.brand-local {
  color: var(--color-ink-soft);
  font-size: 13px;
  font-weight: 500;
}

.desktop-nav {
  display: flex;
  align-items: center;
  gap: 25px;
}

.desktop-nav a {
  color: var(--color-ink);
  font-size: 14px;
  font-weight: 520;
  text-decoration: none;
}

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

.desktop-nav a.is-active,
.desktop-nav a[aria-current="page"] {
  font-weight: 720;
}

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

.language-menu {
  position: relative;
}

.language-trigger {
  min-height: 40px;
  padding: 8px 6px;
  border: 0;
  background: transparent;
  color: var(--color-ink-soft);
  font-size: 13px;
}

.language-trigger:hover {
  color: var(--color-ink);
}

.language-popover {
  position: absolute;
  top: calc(100% + 10px);
  right: 0;
  z-index: 120;
  display: none;
  width: 168px;
  padding: 7px;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-medium);
  background: var(--color-canvas);
  box-shadow: 0 12px 30px var(--color-shadow-soft);
}

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

.language-popover a {
  display: block;
  min-height: 40px;
  padding: 9px 11px;
  border-radius: var(--radius-small);
  color: var(--color-ink);
  font-size: 13px;
  text-decoration: none;
}

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

.header-login {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  justify-content: center;
  padding: 9px 21px;
  border-radius: var(--radius-small);
  background: var(--color-ink);
  color: var(--color-canvas);
  font-size: 13.5px;
  font-weight: 650;
  text-decoration: none;
}

.header-login:hover {
  color: var(--color-canvas);
  opacity: 0.86;
}

.menu-toggle {
  display: none;
  width: 44px;
  min-width: 44px;
  height: 44px;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  padding: 0;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-small);
  background: var(--color-canvas);
}

.menu-toggle-lines,
.menu-toggle-lines::before,
.menu-toggle-lines::after {
  width: 19px;
  height: 1.5px;
  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-drawer {
  position: absolute;
  top: var(--header-height);
  right: 0;
  left: 0;
  z-index: 111;
  display: none;
  max-height: calc(100dvh - var(--header-height));
  overflow-y: auto;
  overscroll-behavior: contain;
  border-bottom: 1px solid var(--color-line);
  background: var(--color-canvas);
  -webkit-overflow-scrolling: touch;
}

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

.mobile-drawer-inner {
  padding: 10px var(--gutter) 24px;
}

.mobile-drawer a {
  display: flex;
  width: 100%;
  min-height: 48px;
  align-items: center;
  padding: 12px 4px;
  border-bottom: 1px solid var(--color-line);
  color: var(--color-ink);
  text-decoration: none;
}

.mobile-drawer a.is-active,
.mobile-drawer a[aria-current="page"] {
  color: var(--color-accent);
  font-weight: 700;
}

.mobile-language-label {
  margin: 20px 0 4px;
  color: var(--color-ink-soft);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
}

.mobile-language-links a {
  font-size: 14px;
}

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

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

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

.footer-main {
  display: grid;
  grid-template-columns: minmax(240px, 1.25fr) repeat(3, minmax(150px, 1fr));
  gap: clamp(36px, 6vw, 84px);
  padding-top: 72px;
  padding-bottom: 58px;
}

.footer-brand {
  max-width: 340px;
}

.footer-brand .site-brand {
  margin-bottom: 18px;
}

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

.footer-heading {
  margin-bottom: 16px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.13em;
  text-transform: uppercase;
}

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

.footer-links a {
  color: var(--color-ink-soft);
  font-size: 14px;
  text-decoration: none;
}

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

.footer-bottom {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding-top: 22px;
  padding-bottom: 26px;
  border-top: 1px solid var(--color-line);
  color: var(--color-ink-soft);
  font-size: 12px;
}

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

.footer-legal a {
  color: var(--color-ink-soft);
  text-decoration: none;
}

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

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

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

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

.prose {
  color: var(--color-ink);
  font-size: 17px;
  line-height: 1.85;
}

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

.prose h2 {
  margin-top: 2.25em;
}

.prose h3 {
  margin-top: 1.8em;
}

.prose blockquote {
  margin-inline: 0;
}

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

@media (max-width: 1180px) {
  .desktop-nav {
    gap: 17px;
  }

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

  .site-header-inner {
    gap: 22px;
  }

  .brand-local {
    display: none;
  }
}

@media (max-width: 980px) {
  .desktop-nav,
  .language-menu {
    display: none;
  }

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

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

  .footer-main {
    grid-template-columns: 1.3fr 1fr 1fr;
  }

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

@media (max-width: 768px) {
  :root {
    --gutter: 20px;
    --toc-offset: 70px;
  }

  h1,
  .display-title {
    font-size: clamp(32px, 9vw, 40px);
    line-height: 1.14;
  }

  h2 {
    font-size: clamp(30px, 8vw, 40px);
  }

  .section {
    padding-top: 72px;
    padding-bottom: 72px;
  }

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

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

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

  body {
    overflow-x: clip;
  }

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

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

  .brand-local {
    display: none;
  }

  .button-row,
  .button,
  .btn-main,
  .btn-sub {
    width: 100%;
  }

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

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

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

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

  .prose {
    font-size: 16px;
  }

  .absolute-decoration,
  .hero-watermark,
  .decorative-orb,
  .decorative-disc {
    display: none;
  }
}

@media (max-width: 380px) {
  .brand-word {
    font-size: 16px;
  }

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

  .site-header-inner {
    gap: 8px;
  }

  .header-tools {
    gap: 6px;
  }

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

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

  *,
  *::before,
  *::after {
    animation: none !important;
    scroll-behavior: auto !important;
    transition: none !important;
  }

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