:root {
  --color-page: #F4F4F6;
  --color-panel: #FFFFFF;
  --color-panel-soft: #ECEDEF;
  --color-border: #D6D8DD;
  --color-border-strong: #B9BDC6;
  --color-brand: #FF681F;
  --color-brand-dark: #C9470E;
  --color-action: #1769E8;
  --color-action-dark: #1055C3;
  --color-text: #111216;
  --color-muted: #626671;
  --color-faint: #8B8F98;
  --color-cyan: #0AAFC4;
  --color-warn: #E85B18;
  --color-error: #C83B45;
  --color-white: #FFFFFF;
  --color-overlay: rgba(17, 18, 22, 0.38);
  --color-brand-wash: rgba(255, 104, 31, 0.10);
  --color-action-wash: rgba(23, 105, 232, 0.09);
  --color-cyan-wash: rgba(10, 175, 196, 0.10);
  --color-panel-glass: rgba(255, 255, 255, 0.78);
  --color-line-glass: rgba(185, 189, 198, 0.78);
  --color-grid: rgba(214, 216, 221, 0.44);
  --color-shadow: rgba(17, 18, 22, 0.10);
  --color-shadow-soft: rgba(17, 18, 22, 0.05);
  --color-action-shadow: rgba(23, 105, 232, 0.18);
  --color-brand-shadow: rgba(255, 104, 31, 0.22);
  --color-flag-red: #D83A42;
  --color-flag-blue: #254D9A;
  --color-flag-dark: #17243E;
  --color-flag-yellow: #F1CB45;
  --color-flag-green: #26885D;

  --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", "SFMono-Regular", Consolas, monospace;

  --radius-xs: 4px;
  --radius-sm: 7px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-pill: 999px;

  --shadow-nav: 0 1px 0 rgba(17, 18, 22, 0.08);
  --shadow-button: 0 8px 20px var(--color-action-shadow);
  --shadow-panel: 0 18px 44px var(--color-shadow-soft);
  --shadow-device: 0 24px 60px var(--color-shadow), 0 3px 10px var(--color-shadow-soft);
  --shadow-device-edge: 0 8px 0 var(--color-shadow-soft);

  --page-width: 1280px;
  --reading-width: 768px;
  --nav-height: 72px;
  --gutter: clamp(16px, 4vw, 32px);
  --section-space: clamp(64px, 8vw, 112px);
  --toc-top: 84px;
  --toc-height: 56px;
  --ease-standard: cubic-bezier(0.2, 0.8, 0.2, 1);
}

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

html {
  min-width: 320px;
  scroll-behavior: smooth;
  background: var(--color-page);
}

html.nav-open {
  overflow: hidden;
}

body {
  min-width: 320px;
  min-height: 100vh;
  margin: 0;
  overflow-x: clip;
  background: var(--color-page);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.68;
  text-rendering: optimizeLegibility;
}

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

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

img {
  height: auto;
}

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

a:not([class]) {
  color: var(--color-action);
  text-decoration: underline;
  text-underline-offset: 0.16em;
}

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

button,
summary {
  cursor: pointer;
}

button {
  color: inherit;
}

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

code {
  overflow-wrap: anywhere;
}

pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 18px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-panel-soft);
  -webkit-overflow-scrolling: touch;
}

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

table {
  border-collapse: collapse;
}

th,
td {
  text-align: left;
}

::selection {
  background: var(--color-brand-wash);
  color: var(--color-text);
}

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

.reading-wrap {
  width: min(100%, 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-tight {
  padding-top: calc(var(--section-space) * 0.58);
  padding-bottom: calc(var(--section-space) * 0.58);
}

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

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

h1,
h2,
h3,
h4 {
  margin-top: 0;
  color: var(--color-text);
  font-family: var(--font-display);
  font-weight: 850;
  line-height: 1.16;
  text-wrap: balance;
}

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

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

h3 {
  margin-bottom: 14px;
  font-size: clamp(22px, 2.4vw, 30px);
  letter-spacing: -0.012em;
}

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

p {
  margin-top: 0;
  margin-bottom: 1.15em;
}

.lead {
  color: var(--color-muted);
  font-size: clamp(18px, 2vw, 22px);
  line-height: 1.62;
}

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

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

.keep-together {
  white-space: nowrap;
}

.kicker {
  display: inline-flex;
  max-width: 100%;
  align-items: center;
  gap: 8px;
  padding: 5px 11px 5px 8px;
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-pill);
  background: var(--color-panel-glass);
  color: var(--color-muted);
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.kicker-dot,
.status-dot {
  width: 8px;
  height: 8px;
  flex: 0 0 auto;
  border-radius: var(--radius-pill);
  background: var(--color-brand);
  box-shadow: 0 0 0 4px var(--color-brand-wash);
}

.title-accent {
  color: var(--color-brand);
}

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

.button,
.cta {
  min-height: 46px;
  padding: 0 22px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  font-size: 15px;
  font-weight: 780;
  line-height: 1.2;
  text-align: center;
  transition:
    color 160ms var(--ease-standard),
    background-color 160ms var(--ease-standard),
    border-color 160ms var(--ease-standard),
    transform 160ms var(--ease-standard),
    box-shadow 160ms var(--ease-standard);
}

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

.button:focus-visible,
.cta:focus-visible,
.nav-link:focus-visible,
.more-trigger:focus-visible,
.language-trigger:focus-visible,
.menu-toggle:focus-visible {
  outline: 3px solid var(--color-action-wash);
  outline-offset: 2px;
}

.button-primary,
.cta-primary {
  color: var(--color-white);
  background: var(--color-action);
  box-shadow: var(--shadow-button);
}

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

.button-secondary,
.cta-secondary {
  border-color: var(--color-border-strong);
  color: var(--color-text);
  background: var(--color-panel);
  box-shadow: 0 4px 12px var(--color-shadow-soft);
}

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

.button-brand {
  color: var(--color-white);
  background: var(--color-brand);
  box-shadow: 0 8px 20px var(--color-brand-shadow);
}

.button-quiet {
  border-color: var(--color-border);
  color: var(--color-muted);
  background: var(--color-panel-soft);
}

.button[disabled],
.button.is-disabled {
  cursor: not-allowed;
  opacity: 0.48;
  transform: none;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

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

.nav-shell {
  width: min(100%, calc(var(--page-width) + (var(--gutter) * 2)));
  min-height: var(--nav-height);
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: grid;
  grid-template-columns: minmax(190px, 250px) 1fr auto;
  align-items: center;
  gap: 24px;
}

.brand {
  width: max-content;
  max-width: 100%;
  display: inline-flex;
  align-items: center;
  gap: 11px;
}

.brand-logo {
  width: 38px;
  height: 38px;
  flex: 0 0 auto;
  border-radius: var(--radius-sm);
  box-shadow: 0 5px 12px var(--color-brand-shadow);
}

.brand-copy {
  min-width: 0;
  display: flex;
  align-items: baseline;
  gap: 8px;
  white-space: nowrap;
}

.brand-en {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 850;
  letter-spacing: -0.02em;
}

.brand-local {
  color: var(--color-muted);
  font-size: 13px;
  font-weight: 550;
}

.desktop-nav {
  height: var(--nav-height);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
}

.nav-link,
.more-trigger {
  min-height: 40px;
  padding: 0 13px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 0;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--color-muted);
  font-size: 14px;
  font-weight: 650;
  white-space: nowrap;
}

.nav-link:hover,
.more-trigger:hover,
.nav-link.is-active {
  color: var(--color-text);
  background: var(--color-panel-soft);
}

.nav-link.is-active {
  border-radius: 0;
  box-shadow: inset 0 -2px 0 var(--color-brand);
}

.more-menu,
.language-menu {
  position: relative;
}

.more-menu {
  height: var(--nav-height);
  display: flex;
  align-items: center;
}

.more-popover,
.language-popover {
  position: absolute;
  top: calc(100% - 10px);
  padding: 7px;
  visibility: hidden;
  opacity: 0;
  transform: translateY(-4px);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-panel);
  box-shadow: var(--shadow-device);
  transition: opacity 160ms var(--ease-standard), transform 160ms var(--ease-standard);
}

.more-popover {
  left: 0;
  width: 154px;
}

.language-popover {
  right: 0;
  width: 142px;
}

.more-menu:hover .more-popover,
.more-menu:focus-within .more-popover,
.language-menu.is-open .language-popover {
  visibility: visible;
  opacity: 1;
  transform: translateY(0);
}

.more-popover a,
.language-popover a {
  min-height: 40px;
  padding: 8px 11px;
  display: flex;
  align-items: center;
  border-radius: var(--radius-xs);
  color: var(--color-muted);
  font-size: 13px;
  font-weight: 620;
}

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

.nav-tools {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 8px;
}

.language-trigger {
  min-height: 40px;
  padding: 0 9px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  border: 0;
  border-radius: var(--radius-sm);
  color: var(--color-muted);
  background: transparent;
  font-size: 13px;
  font-weight: 600;
  white-space: nowrap;
}

.language-trigger:hover {
  color: var(--color-text);
  background: var(--color-panel-soft);
}

.login-button {
  min-height: 40px;
  padding: 0 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--color-action);
  border-radius: var(--radius-sm);
  color: var(--color-action);
  background: var(--color-panel);
  font-size: 14px;
  font-weight: 760;
  white-space: nowrap;
}

.login-button:hover {
  color: var(--color-white);
  background: var(--color-action);
}

.menu-toggle {
  min-width: 44px;
  min-height: 44px;
  padding: 10px;
  display: none;
  align-items: center;
  justify-content: center;
  border: 0;
  border-radius: var(--radius-sm);
  background: var(--color-panel-soft);
}

.menu-toggle-lines,
.menu-toggle-lines::before,
.menu-toggle-lines::after {
  width: 20px;
  height: 2px;
  display: block;
  border-radius: var(--radius-pill);
  background: var(--color-text);
}

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

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

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

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

.menu-toggle[aria-expanded="true"] .menu-toggle-lines {
  background: transparent;
}

.menu-toggle[aria-expanded="true"] .menu-toggle-lines::before {
  top: 0;
  transform: rotate(45deg);
}

.menu-toggle[aria-expanded="true"] .menu-toggle-lines::after {
  top: 0;
  transform: rotate(-45deg);
}

.mobile-nav {
  position: absolute;
  z-index: 102;
  top: var(--nav-height);
  left: 0;
  right: 0;
  display: none;
  max-height: calc(100dvh - var(--nav-height));
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 12px var(--gutter) 20px;
  border-top: 1px solid var(--color-border);
  background: var(--color-panel);
  box-shadow: var(--shadow-device);
}

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

.mobile-nav a {
  width: 100%;
  min-height: 46px;
  padding: 11px 12px;
  display: flex;
  align-items: center;
  border-radius: var(--radius-sm);
  color: var(--color-muted);
  font-size: 15px;
  font-weight: 650;
}

.mobile-nav a:hover,
.mobile-nav a.is-active {
  color: var(--color-text);
  background: var(--color-panel-soft);
}

.mobile-language {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--color-border);
}

.mobile-language-label {
  padding: 8px 12px;
  color: var(--color-faint);
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

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

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

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

.footer-main {
  padding-top: 58px;
  padding-bottom: 42px;
  display: grid;
  grid-template-columns: minmax(260px, 1.35fr) repeat(3, minmax(150px, 1fr));
  gap: 42px;
}

.footer-brand p {
  max-width: 440px;
  margin-top: 18px;
  color: var(--color-muted);
  font-size: 14px;
}

.footer-column h2 {
  margin-bottom: 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.footer-links {
  display: grid;
  gap: 8px;
}

.footer-links a {
  width: fit-content;
  max-width: 100%;
  color: var(--color-muted);
  font-size: 14px;
}

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

.footer-bottom {
  padding-top: 20px;
  padding-bottom: 22px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 16px 24px;
  border-top: 1px solid var(--color-border);
  color: var(--color-muted);
  font-size: 13px;
}

.footer-legal {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 18px;
}

.reveal {
  transition: opacity 560ms var(--ease-standard), transform 560ms var(--ease-standard);
}

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

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

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

.prose h2,
.prose h3,
.prose h4 {
  scroll-margin-top: calc(var(--toc-top) + var(--toc-height) + 20px);
}

.prose p,
.prose li {
  overflow-wrap: break-word;
}

.prose blockquote {
  margin: 24px 0;
}

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

.prose img {
  margin-inline: auto;
}

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

body:has(.toc-tabs) section[id] {
  scroll-margin-top: calc(var(--toc-top) + var(--toc-height) + 20px);
}

@media (max-width: 1020px) {
  .nav-shell {
    grid-template-columns: auto 1fr auto;
    gap: 14px;
  }

  .desktop-nav {
    display: none;
  }

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

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

  .footer-main {
    grid-template-columns: 1.25fr 1fr 1fr;
  }

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

@media (max-width: 768px) {
  :root {
    --nav-height: 64px;
    --toc-top: 72px;
  }

  h1,
  .hero-title {
    font-size: clamp(28px, 9.5vw, 40px);
    line-height: 1.12;
    letter-spacing: -0.015em;
  }

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

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

  .nav-shell {
    gap: 8px;
  }

  .login-button {
    min-width: 64px;
    padding-inline: 12px;
  }

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

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

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

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

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

  body {
    overflow-x: clip;
  }

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

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

  .section-tight {
    padding-top: 40px;
    padding-bottom: 40px;
  }

  .tilt,
  .tilt-card {
    transform: none;
  }

  .absolute-decoration,
  .hero-decoration,
  [data-decorative-absolute] {
    max-width: 100%;
    transform: none;
  }

  .button-row .button,
  .button-row .cta {
    flex: 1 1 100%;
  }

  .footer-main {
    grid-template-columns: 1fr;
    gap: 28px;
  }

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

  .footer-links a {
    width: 100%;
    min-height: 40px;
    display: flex;
    align-items: center;
  }
}

@media (max-width: 390px) {
  .brand-copy {
    display: none;
  }

  .login-button {
    min-width: 58px;
    padding-inline: 10px;
    font-size: 13px;
  }

  .nav-tools {
    gap: 5px;
  }
}

@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;
  }
}