:root {
  --site-nav-x: 20px;
  --site-nav-border: #1a1a1a;
  --site-nav-bg-scrolled: rgba(10, 10, 10, 0.9);
  --site-nav-muted: #555;
  --site-nav-hover: #ccc;
  --site-nav-prefix: #444;
  --site-nav-accent: #6fb6a6;
}

main {
  padding-top: 0;
}

.topbar,
.topbar.is-compact,
.topbar.is-scrolled,
.topbar.scrolled {
  position: sticky;
  top: 0;
  z-index: 60;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  min-height: 0;
  padding: 1rem var(--site-nav-x);
  background: transparent;
  border-bottom: 1px solid transparent;
  -webkit-backdrop-filter: none;
  backdrop-filter: none;
  transition:
    background 0.4s,
    padding 0.4s,
    border-color 0.4s;
}

.topbar.is-compact,
.topbar.is-scrolled,
.topbar.scrolled {
  padding-top: 0.6rem;
  padding-bottom: 0.6rem;
  background: var(--site-nav-bg-scrolled);
  border-bottom-color: var(--site-nav-border);
  -webkit-backdrop-filter: blur(16px);
  backdrop-filter: blur(16px);
}

.brand,
.topbar.is-compact .brand {
  flex-shrink: 0;
  gap: 0;
  color: #fff;
}

.brand-mark,
.brand small,
.topbar.is-compact .brand-mark,
.topbar.is-compact .brand small {
  display: none;
}

.brand strong {
  display: block;
  color: #fff;
  font-family: var(--heading-font);
  font-size: 1.25rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  line-height: 1;
  text-transform: none;
}

.brand .brand-wordmark {
  display: flex;
  align-items: baseline;
}

.brand .brand-const {
  color: var(--site-nav-accent);
}

.brand strong::before {
  content: "> ";
  color: var(--site-nav-prefix);
  font-weight: 400;
}

.brand:hover {
  color: rgba(255, 255, 255, 0.7);
}

.nav,
.topbar.is-compact .nav,
.topbar.is-scrolled .nav,
.topbar.scrolled .nav {
  display: flex;
  flex: 1;
  align-items: center;
  justify-content: flex-end;
  gap: 0.78rem;
  min-width: 0;
}

.nav > a,
.topbar.is-compact .nav > a,
.topbar.is-scrolled .nav > a,
.topbar.scrolled .nav > a {
  display: block;
  padding: 0;
  color: var(--site-nav-muted);
  font-family: var(--heading-font);
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.06em;
  line-height: 1.4;
  text-transform: uppercase;
  white-space: nowrap;
}

.nav > a:hover {
  color: var(--site-nav-hover);
}

.nav-toggle,
.topbar.is-compact .nav-toggle,
.topbar.is-scrolled .nav-toggle,
.topbar.scrolled .nav-toggle {
  display: none;
  margin-left: auto;
  padding: 4px;
  width: 2rem;
  height: 2rem;
  border: 0;
  color: #666;
  background: transparent;
  cursor: pointer;
  transition: color 0.2s;
}

.nav-toggle:hover {
  color: var(--site-nav-hover);
}

.nav-toggle span {
  height: 1px;
  margin: 0.34rem 0;
  background: currentColor;
}

.lang-switcher {
  position: relative;
  display: flex;
  align-items: center;
  flex-shrink: 0;
  margin-left: 0.25rem;
  padding-left: 0.7rem;
  border-left: 1px solid var(--site-nav-border);
}

.lang-trigger,
.topbar.is-compact .lang-trigger,
.topbar.is-scrolled .lang-trigger,
.topbar.scrolled .lang-trigger {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  min-height: 0;
  padding: 0.35rem 0.7rem;
  border: 1px solid #222;
  color: var(--site-nav-muted);
  background: transparent;
  font-family: var(--heading-font);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: none;
  cursor: pointer;
  transition: color 0.2s, border-color 0.2s;
}

.lang-trigger:hover,
.lang-switcher.open .lang-trigger,
.lang-switcher.is-open .lang-trigger {
  color: var(--site-nav-hover);
  border-color: #444;
}

.lang-chevron {
  transition: transform 0.2s;
}

.lang-switcher.open .lang-chevron,
.lang-switcher.is-open .lang-chevron {
  transform: rotate(180deg);
}

.lang-panel {
  top: calc(100% + 0.4rem);
  right: 0;
  min-width: 150px;
  background: #111;
  border: 1px solid #222;
  z-index: 100;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.6);
}

.lang-switcher.open .lang-panel,
.lang-switcher.is-open .lang-panel {
  display: block;
}

.lang-panel-header {
  padding: 0.6rem 0.8rem 0.3rem;
  color: var(--site-nav-prefix);
  font-size: 0.5625rem;
  letter-spacing: 0.12em;
}

.lang-option,
.lang-switcher .lang-option {
  gap: 0.5rem;
  padding: 0.5rem 0.8rem;
  color: #666;
  font-size: 0.75rem;
  letter-spacing: 0;
}

.lang-option:hover {
  background: rgba(255, 255, 255, 0.04);
  color: var(--site-nav-hover);
}

.lang-option-code {
  color: var(--site-nav-prefix);
  font-size: 0.625rem;
}

.lang-option.active,
.lang-switcher .lang-option.active {
  color: var(--site-nav-hover);
}

.lang-check {
  color: var(--site-nav-accent);
}

.medical-notice {
  width: fit-content;
  max-width: min(72rem, calc(100vw - (var(--site-nav-x) * 2)));
  margin: 0.75rem var(--site-nav-x) clamp(1rem, 2vw, 1.5rem);
  padding: 0.6rem 0.75rem;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: rgba(17, 22, 21, 0.38);
  color: rgba(255, 255, 255, 0.48);
}

.medical-notice p {
  margin: 0;
  max-width: 72rem;
  color: inherit;
  font-family: var(--heading-font);
  font-size: 0.72rem;
  line-height: 1.55;
  letter-spacing: 0.04em;
  text-align: left;
}

html[data-lang^="zh"] .nav > a,
html[data-lang="ja"] .nav > a,
html[data-lang^="zh"] .medical-notice p,
html[data-lang="ja"] .medical-notice p {
  letter-spacing: 0.04em;
  text-transform: none;
}

@media (max-width: 1199px) {
  .topbar,
  .topbar.is-compact,
  .topbar.is-scrolled,
  .topbar.scrolled {
    flex-wrap: wrap;
  }

  .nav-toggle,
  .topbar.is-compact .nav-toggle,
  .topbar.is-scrolled .nav-toggle,
  .topbar.scrolled .nav-toggle {
    display: block;
  }

  .nav,
  .topbar.is-compact .nav,
  .topbar.is-scrolled .nav,
  .topbar.scrolled .nav {
    display: none;
    width: calc(100vw - (var(--site-nav-x) * 2));
    max-width: 100%;
    flex: 0 0 100%;
    flex-direction: column;
    align-items: flex-start;
    justify-content: flex-start;
    gap: 0.75rem;
    margin-top: 0;
    padding-top: 1rem;
  }

  .nav.open,
  .nav.is-open,
  .topbar.is-compact .nav.open,
  .topbar.is-compact .nav.is-open,
  .topbar.is-scrolled .nav.open,
  .topbar.is-scrolled .nav.is-open,
  .topbar.scrolled .nav.open,
  .topbar.scrolled .nav.is-open {
    display: flex;
  }

  .nav > a,
  .topbar.is-compact .nav > a,
  .topbar.is-scrolled .nav > a,
  .topbar.scrolled .nav > a {
    padding: 0;
    text-align: left;
    font-size: 0.8125rem;
    line-height: 1.2;
  }

  .lang-switcher {
    width: 100%;
    margin: 0;
    padding: 0;
    border-left: 0;
  }

  .lang-trigger {
    width: 100%;
    justify-content: space-between;
  }

  .lang-panel {
    position: static;
    width: 100%;
    min-width: 0;
    margin-top: 0.5rem;
    box-shadow: none;
  }
}

@media (max-width: 560px) {
  :root {
    --site-nav-x: 16px;
  }

  .brand strong {
    font-size: 1.05rem;
  }

  .medical-notice p {
    font-size: 0.68rem;
  }

  .medical-notice {
    width: auto;
  }
}