.floating-rail {
  position: fixed;
  top: 18px;
  right: 18px;
  z-index: 20;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.mobile-menu-toggle {
  display: none;
  position: fixed;
  top: 12px;
  right: 12px;
  z-index: 10100;
  isolation: isolate;
  width: 44px;
  height: 44px;
  border: 0;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
  cursor: pointer;
}

.mobile-font-tools {
  display: none;
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 10100;
  isolation: isolate;
  gap: 6px;
}

.burger-line {
  position: absolute;
  left: 10px;
  width: 24px;
  height: 2px;
  border-radius: 999px;
  background: var(--primary-jade);
  transition: transform .28s ease, opacity .2s ease, top .28s ease;
}

.burger-line:nth-child(1) { top: 14px; }
.burger-line:nth-child(2) { top: 21px; }
.burger-line:nth-child(3) { top: 28px; }

.mobile-menu-toggle.open .burger-line:nth-child(1) {
  top: 21px;
  transform: rotate(45deg);
}

.mobile-menu-toggle.open .burger-line:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.open .burger-line:nth-child(3) {
  top: 21px;
  transform: rotate(-45deg);
}

.mobile-menu-backdrop {
  position: fixed;
  inset: 0;
  z-index: 10090;
  background: rgba(0,0,0,.28);
  opacity: 0;
  pointer-events: none;
  transition: opacity .24s ease;
}

.mobile-menu-backdrop.open {
  opacity: 1;
  pointer-events: auto;
}

.mobile-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 100vh;
  height: 100dvh;
  z-index: 10095;
  pointer-events: none;
}

.mobile-nav-panel {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  min-height: 60vh;
  min-height: 60dvh;
  max-height: 74vh;
  max-height: 74dvh;
  background: rgba(206, 211, 195, 0.2);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border: 1px solid rgba(40, 56, 49, 0.2);
  border-radius: 3em 3em 0 0;
  box-shadow:
    0 -22px 60px rgba(28, 74, 60, 0.32),
    0 -10px 28px rgba(28, 74, 60, 0.2),
    0 -2px 8px rgba(0, 0, 0, 0.12),
    inset 0 1px 0 rgba(255, 255, 255, 0.55);
  padding: 78px 14px 14px;
  display: flex;
  flex-direction: column;
  overflow: visible !important;
  transform: translateY(140px) scale(.94);
  opacity: 0;
  transition: transform .9s cubic-bezier(.16,.9,.2,1), opacity .7s ease;
}

.mobile-nav.open {
  pointer-events: auto;
  background-color: var(--paper-veil);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
}

.mobile-nav.open .mobile-nav-panel {
  transform: translateY(0) scale(1);
  opacity: 1;
}

.mobile-nav-brand.side-nav-brand {
  flex-direction: row;
  align-items: center;
  justify-content: flex-start;
  align-self: flex-start;
  width: auto;
  max-width: calc(100% - 24px);
  margin-top: 0;
  margin-bottom: 0;
  gap: 2px;
}

.mobile-nav-brand {
  display: flex;
  align-items: center;
  gap: 2px;
  position: absolute;
  top: -34px;
  left: 10px;
  right: auto;
  z-index: 5;
  font-family: "Noto Serif TC", serif;
  font-size: clamp(22px, 6.5vw, 28px);
  font-weight: 700;
  color: var(--ink-85);
  text-decoration: none;
  transition:
    transform 0.28s ease,
    opacity 0.28s ease,
    visibility 0.28s ease;
  pointer-events: none;
  visibility: hidden;
  opacity: 0;
}

.mobile-nav.open .mobile-nav-brand {
  pointer-events: auto;
  visibility: visible;
  opacity: 1;
}

.mobile-nav.open .mobile-nav-brand:hover {
  transform: translateY(-2px);
  opacity: 0.9;
}

.mobile-nav-brand img {
  width: clamp(52px, 14vw, 68px);
  height: auto;
  flex-shrink: 0;
  display: block;
  filter: drop-shadow(0 6px 14px rgba(28, 74, 60, 0.22));
}

.mobile-nav-brand span {
  line-height: 1.1;
  white-space: nowrap;
}

.mobile-main-links {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 0;
}

.mobile-primary-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 22px 14px;
  width: min(100%, 520px);
  margin: 0 auto;
}

.mobile-primary-grid .nav-item {
  font-size: 18px;
  line-height: 1.4;
  padding: 8px 6px;
}

.mobile-primary-grid .nav-icon {
  width: 64px;
  height: 64px;
  margin-bottom: 10px;
}

.mobile-nav-divider {
  margin: 12px 0 10px;
  border-top: 1px solid rgba(44,44,44,.2);
}

.mobile-nav-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-top: 2px;
}

.mobile-nav-meta .english-link {
  margin: 0;
  padding: 0;
  width: auto;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  letter-spacing: .04em;
}

.mobile-nav-meta .english-link .nav-icon {
  height: 2em;
  margin: 0;
}

.side-nav {
  position: relative;
  width: var(--rail-w);
  padding: 14px 8px 20px;
  background: rgba(206, 211, 195, 0.94);
  backdrop-filter: var(--blur);
  -webkit-backdrop-filter: var(--blur);
  border: 1px solid rgba(40, 56, 49, 0.18);
  box-shadow:
    0 22px 44px rgba(28, 74, 60, 0.24),
    0 10px 20px rgba(28, 74, 60, 0.16),
    0 2px 6px rgba(0, 0, 0, 0.08),
    inset 0 1px 0 rgba(255, 255, 255, 0.6);
  border-radius: 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
  margin-top: 2em;
}

.side-nav::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: var(--jade-gradient);
  opacity: 0.08;
  z-index: -1;
}

.side-nav-brand {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 100%;
  margin-top: -2em;
  margin-bottom: 2px;
  text-decoration: none;
  color: inherit;
  transition: transform 0.28s ease, opacity 0.28s ease;
}

.side-nav-brand:hover {
  transform: translateY(-2px);
  opacity: 0.92;
}

.side-logo {
  width: 64px;
  display: block;
  margin-bottom: 2px;
}

.side-logo-text {
  display: block;
  margin-top: -4px;
  margin-bottom: -2px;
  line-height: 1.1;
  font-size: 16px;
  font-family: "Noto Serif TC", serif;
  font-weight: bolder;
}

.nav-item {
  width: 100%;
  text-align: center;
  font-size: 12px;
  color: var(--ink-70);
  line-height: 1.35;
  transition: color .25s ease, transform .25s ease;
}

.nav-item:hover {
  color: var(--primary-jade);
  transform: translateY(-1px);
}

.nav-item:focus-visible,
.side-nav-brand:focus-visible,
.mobile-menu-toggle:focus-visible {
  outline: none;
  box-shadow: var(--focus);
  border-radius: 8px;
}

@media (min-width: 861px) and (min-height: 501px) {
  .mobile-nav,
  .mobile-menu-backdrop {
    visibility: hidden;
  }
}

.nav-icon {
  width: 38px;
  height: 38px;
  margin: 0 auto 5px;
  display: grid;
  place-items: center;
  font-size: 22px;
  color: var(--ink-70);
  font-family: sans-serif;
}

.nav-icon img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.side-nav .nav-item:first-of-type {
  margin-top: -8px;
}

.nav-item.english-link {
  margin-top: 10px;
  padding-top: 10px;
  font-size: 1em;
  letter-spacing: 0.08em;
}

/* 側邊欄是 position: fixed，不在 main 的 zoom 範圍內，
   因此字級需自行乘上 --font-scale 才會隨字級調整鈕變化。
   只放大文字，不動 --rail-w，欄寬與圖示維持原尺寸。 */
.side-nav .nav-item {
  font-size: calc(12px * var(--font-scale, 1));
}

.side-nav .side-logo-text {
  font-size: calc(16px * var(--font-scale, 1));
}

.font-tools {
  display: flex;
  flex-direction: row;
  justify-content: center;
  width: 100%;
  margin-top: 2px;
  padding-top: 10px;
  border-top: 1px solid var(--rule);
  gap: 6px;
}

@media (max-width: 860px),
       ((max-width: 1024px) and (max-height: 500px) and (pointer: coarse)) {
  .floating-rail { display: none; }

  .mobile-menu-toggle {
    display: inline-grid;
    place-items: center;
    background: rgba(255, 255, 255, 0.85);
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(28, 74, 60, 0.18);
  }
  .mobile-menu-toggle.open { background: rgba(255, 255, 255, 0.95); }

  .mobile-font-tools {
    display: flex;
    top: 10px;
    left: 10px;
    gap: 8px;
  }

  .mobile-font-tools .font-btn {
    width: 44px;
    height: 44px;
    min-height: 44px;
    font-size: 18px;
    background: rgba(255, 255, 255, 0.95);
    box-shadow: 0 4px 12px rgba(28, 74, 60, 0.18);
  }

  .mobile-nav.open .mobile-nav-brand {
    left: 8px;
    top: -30px;
    z-index: 6;
  }
}

@media (orientation: landscape) and (max-height: 500px) and (pointer: coarse) {
  .mobile-nav-panel {
    top: 0;
    right: 0;
    left: auto;
    bottom: 0;
    width: min(320px, 84vw);
    height: 100dvh;
    min-height: 0;
    max-height: none;
    border-radius: 1.25em 0 0 1.25em;
    padding:
      calc(14px + env(safe-area-inset-top, 0px))
      calc(16px + env(safe-area-inset-right, 0px))
      calc(14px + env(safe-area-inset-bottom, 0px))
      16px;
    gap: 10px;
    transform: translateX(105%);
    opacity: 1;
  }

  .mobile-nav.open .mobile-nav-panel {
    transform: translateX(0);
  }

  .mobile-nav-brand {
    position: static;
    top: auto;
    left: auto;
    font-size: 20px;
    margin-bottom: 2px;
    flex-shrink: 0;
  }

  .mobile-nav.open .mobile-nav-brand {
    top: auto;
    left: auto;
  }

  .mobile-nav-brand img {
    width: 44px;
  }

  .mobile-main-links {
    flex: 1;
    align-items: stretch;
    justify-content: center;
    min-height: 0;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }

  .mobile-primary-grid {
    grid-template-columns: 1fr 1fr;
    gap: 10px 12px;
    width: 100%;
    margin: 0;
  }

  .mobile-primary-grid .nav-item {
    font-size: 15px;
    line-height: 1.35;
    padding: 8px 4px;
  }

  .mobile-primary-grid .nav-icon {
    width: 46px;
    height: 46px;
    margin-bottom: 6px;
  }

  .mobile-nav-divider {
    margin: 6px 0 4px;
    flex-shrink: 0;
  }

  .mobile-nav-meta {
    flex-shrink: 0;
    justify-content: flex-start;
    margin-top: 0;
    padding-top: 2px;
  }

  .mobile-nav-meta .english-link {
    font-size: 13px;
  }
}