/* ============================================================
   Apple-Level Liquid Glass Design System
   Inspired by iOS 18 / visionOS Glassmorphism
   ============================================================ */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

:root {
  /* ---- Color Palette ---- */
  --text-main: #1d1d1f;
  --text-muted: #6e6e73;
  --text-tertiary: #aeaeb2;
  --accent-color: #0071e3;       /* Apple Blue */
  --accent-vivid: #007aff;
  --accent-light: rgba(0, 113, 227, 0.08);
  --accent-glow: rgba(0, 113, 227, 0.2);

  /* ---- Glass System ---- */
  --glass-white: rgba(255, 255, 255, 0.72);
  --glass-white-mid: rgba(255, 255, 255, 0.55);
  --glass-white-thin: rgba(255, 255, 255, 0.35);
  --glass-surface: rgba(255, 255, 255, 0.85);
  --glass-blur: blur(40px) saturate(200%);
  --glass-blur-heavy: blur(60px) saturate(220%);
  --glass-blur-light: blur(20px) saturate(180%);

  /* ---- Borders (light-catching effect) ---- */
  --border-glass: 1px solid rgba(255, 255, 255, 0.8);
  --border-glass-outer: 1px solid rgba(180, 190, 210, 0.25);
  --border-divider: 1px solid rgba(0, 0, 0, 0.06);

  /* ---- Shadows ---- */
  --shadow-card: 
    0 2px 4px rgba(0,0,0,0.04),
    0 8px 24px rgba(0,0,0,0.06),
    0 32px 64px rgba(0,0,0,0.06),
    inset 0 1px 0 rgba(255,255,255,0.9);
  --shadow-elevated:
    0 4px 8px rgba(0,0,0,0.06),
    0 16px 40px rgba(0,0,0,0.09),
    inset 0 1px 0 rgba(255,255,255,0.8);
  --shadow-btn:
    0 1px 2px rgba(0,0,0,0.04),
    0 4px 12px rgba(0,0,0,0.06),
    inset 0 1px 0 rgba(255,255,255,0.85);
  --shadow-btn-hover:
    0 2px 6px rgba(0,0,0,0.08),
    0 8px 24px rgba(0,0,0,0.10),
    inset 0 1px 0 rgba(255,255,255,0.9);
  --shadow-btn-pressed:
    0 1px 2px rgba(0,0,0,0.08),
    inset 0 1px 4px rgba(0,0,0,0.06);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.05), 0 4px 12px rgba(0,0,0,0.05);
  --shadow-glow: 0 0 20px rgba(0, 113, 227, 0.25), 0 8px 32px rgba(0, 113, 227, 0.15);

  /* ---- Typography ---- */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", 'Noto Sans SC', sans-serif;

  /* ---- Border Radii ---- */
  --radius-xs: 6px;
  --radius-sm: 12px;
  --radius-md: 18px;
  --radius-lg: 26px;
  --radius-xl: 36px;
  --radius-pill: 999px;

  /* ---- Transitions ---- */
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-smooth: cubic-bezier(0.25, 0.8, 0.25, 1);
  --transition: all 0.28s var(--ease-smooth);
  --transition-spring: all 0.4s var(--ease-spring);
}

/* ============================================================
   BASE & RESET
   ============================================================ */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  position: relative;
}

/* ---- Premium Mesh Gradient Background ---- */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: -2;
  background: #e8eaf0;
}

body::after {
  content: '';
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(ellipse 80% 60% at 10% 20%, rgba(174, 210, 255, 0.75), transparent),
    radial-gradient(ellipse 60% 80% at 90% 80%, rgba(213, 190, 255, 0.65), transparent),
    radial-gradient(ellipse 70% 50% at 50% 100%, rgba(255, 200, 220, 0.5), transparent),
    radial-gradient(ellipse 50% 60% at 80% 10%, rgba(180, 230, 250, 0.6), transparent);
  animation: mesh-drift 20s ease-in-out infinite alternate;
}

@keyframes mesh-drift {
  0%   { opacity: 1; transform: scale(1) translate(0, 0); }
  50%  { opacity: 0.85; transform: scale(1.02) translate(-1%, 1%); }
  100% { opacity: 1; transform: scale(1.04) translate(1%, -1%); }
}

/* ---- Scrollbar ---- */
::-webkit-scrollbar { width: 5px; height: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: rgba(0,0,0,0.15);
  border-radius: var(--radius-pill);
}
::-webkit-scrollbar-thumb:hover { background: rgba(0,0,0,0.25); }

/* ============================================================
   APP LAYOUT
   ============================================================ */
.app-wrapper {
  display: flex;
  width: 100vw;
  height: 100vh;
}

/* ============================================================
   SIDEBAR
   ============================================================ */
.sidebar {
  width: 300px;
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  height: 100%;
  z-index: 10;
  background: var(--glass-white);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-right: var(--border-glass-outer);
  box-shadow: 2px 0 40px rgba(0,0,0,0.04);
  position: relative;
}

/* Inner top-to-bottom light sheen */
.sidebar::before {
  content: '';
  position: absolute;
  inset: 0;
  border-right: var(--border-glass);
  pointer-events: none;
  z-index: 1;
}

.sidebar-header {
  padding: 1.5rem 1.25rem 1.25rem;
  border-bottom: var(--border-divider);
  display: flex;
  align-items: center;
  gap: 0.85rem;
  position: relative;
}

.sidebar-logo {
  font-size: 1.4rem;
  color: white;
}

.sidebar-title h1 {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.2px;
  color: var(--text-main);
}

.sidebar-title span {
  font-size: 0.7rem;
  font-weight: 400;
  color: var(--text-muted);
  display: block;
  letter-spacing: 0.3px;
  margin-top: 1px;
}

/* ---- Sidebar Unit List ---- */
.unit-list {
  flex: 1;
  overflow-y: auto;
  padding: 0.6rem;
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

/* ---- Liquid Glass Unit Item Buttons ---- */
.unit-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 0.9rem;
  border-radius: var(--radius-sm);
  background: transparent;
  border: 1px solid transparent;
  cursor: pointer;
  width: 100%;
  text-align: left;
  font-family: var(--font-sans);
  transition: var(--transition);
  position: relative;
}

.unit-item:hover {
  background: rgba(255, 255, 255, 0.6);
  border-color: rgba(255, 255, 255, 0.8);
  box-shadow: var(--shadow-btn);
}

.unit-item.active {
  background: rgba(255, 255, 255, 0.75);
  border-color: rgba(255, 255, 255, 0.9);
  box-shadow: var(--shadow-btn);
  color: var(--accent-color);
}

.unit-item.active::before {
  content: '';
  position: absolute;
  left: 0;
  top: 20%;
  bottom: 20%;
  width: 3px;
  border-radius: var(--radius-pill);
  background: var(--accent-color);
  box-shadow: 0 0 8px var(--accent-glow);
}

.unit-item-info {
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  max-width: 80%;
}

.unit-item-title {
  font-size: 0.875rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.unit-item-desc {
  font-size: 0.7rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.unit-item.active .unit-item-desc {
  color: var(--accent-color);
  opacity: 0.75;
}

.unit-item-count {
  font-size: 0.7rem;
  background: rgba(0, 0, 0, 0.06);
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-pill);
  font-weight: 600;
  color: var(--text-muted);
  flex-shrink: 0;
}

.unit-item.active .unit-item-count {
  background: var(--accent-color);
  color: white;
  box-shadow: 0 2px 8px var(--accent-glow);
}

/* ---- TOC Word List ---- */
.sidebar-back-header {
  position: sticky;
  top: 0;
  z-index: 2;
  background: rgba(255,255,255,0.6);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  padding: 0.75rem 0.9rem;
  border-bottom: var(--border-divider);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--accent-color);
  font-weight: 600;
  cursor: pointer;
  font-size: 0.875rem;
  transition: var(--transition);
  width: 100%;
  border-left: none;
  border-right: none;
  border-top: none;
  text-align: left;
  font-family: var(--font-sans);
}

.sidebar-back-header:hover {
  background: rgba(255,255,255,0.75);
}

.toc-word-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.65rem 0.9rem;
  font-size: 0.82rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  background: transparent;
  border: 1px solid transparent;
  text-align: left;
  width: 100%;
  font-family: var(--font-sans);
}

.toc-word-item:hover {
  background: rgba(255, 255, 255, 0.55);
  border-color: rgba(255, 255, 255, 0.8);
  box-shadow: var(--shadow-sm);
}

.toc-word-item.active {
  background: rgba(255, 255, 255, 0.75);
  border-color: rgba(255, 255, 255, 0.9);
  color: var(--accent-color);
  font-weight: 600;
  box-shadow: var(--shadow-btn);
}

.toc-word-text {
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 58%;
}

.toc-word-translation {
  font-size: 0.72rem;
  color: var(--text-muted);
  max-width: 38%;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  text-align: right;
}

.toc-word-item.active .toc-word-translation {
  color: var(--accent-color);
  opacity: 0.7;
}

/* ---- Sidebar Bottom Settings ---- */
.sidebar-settings {
  padding: 1rem 1.25rem;
  border-top: var(--border-divider);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
}

/* ============================================================
   MAIN CONTENT AREA
   ============================================================ */
.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100%;
  position: relative;
  overflow: hidden;
}

/* ---- Top Header Bar ---- */
.main-header {
  padding: 0.9rem 2rem;
  background: rgba(255, 255, 255, 0.6);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-bottom: var(--border-divider);
  box-shadow: 0 1px 0 rgba(255,255,255,0.8), 0 4px 20px rgba(0,0,0,0.04);
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 5;
  flex-shrink: 0;
}

/* ---- Apple-style Segmented Control ---- */
.view-mode-selector {
  display: flex;
  background: rgba(0, 0, 0, 0.06);
  padding: 0.2rem;
  border-radius: var(--radius-pill);
  border: var(--border-glass-outer);
}

.mode-btn {
  background: transparent;
  border: none;
  font-family: var(--font-sans);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  padding: 0.38rem 1rem;
  border-radius: var(--radius-pill);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.3rem;
  transition: var(--transition-spring);
}

.mode-btn:hover {
  color: var(--text-main);
}

.mode-btn.active {
  background: white;
  color: var(--text-main);
  box-shadow: var(--shadow-btn);
}

/* ---- Liquid Glass Filter Star & Add to Desktop Buttons ---- */
#filter-star-btn,
#add-to-desktop-btn {
  background: var(--glass-white-mid);
  backdrop-filter: var(--glass-blur-light);
  -webkit-backdrop-filter: var(--glass-blur-light);
  border: var(--border-glass);
  box-shadow: var(--shadow-btn);
  color: var(--text-muted);
  padding: 0.38rem 0.85rem;
  border-radius: var(--radius-pill);
  font-size: 0.82rem;
  transition: var(--transition-spring);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-family: var(--font-sans);
  font-weight: 600;
}

#filter-star-btn:hover,
#add-to-desktop-btn:hover {
  background: rgba(255, 255, 255, 0.85);
  box-shadow: var(--shadow-btn-hover);
  transform: translateY(-1px);
  color: var(--text-main);
}

#filter-star-btn.starred-active {
  background: rgba(251, 191, 36, 0.12);
  border-color: rgba(251, 191, 36, 0.4);
  box-shadow: 0 0 16px rgba(251,191,36,0.2), var(--shadow-btn);
}

/* ---- Custom Action Toast (Premium visionOS capsule look) ---- */
.custom-toast {
  position: fixed;
  bottom: 2.5rem;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: rgba(29, 29, 31, 0.88);
  color: white;
  padding: 0.75rem 1.6rem;
  border-radius: var(--radius-pill);
  font-size: 0.85rem;
  font-weight: 500;
  z-index: 9999;
  opacity: 0;
  transition: opacity 0.3s ease, transform 0.3s var(--ease-spring);
  pointer-events: none;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.25);
  border: 1px solid rgba(255, 255, 255, 0.18);
  letter-spacing: 0.3px;
  white-space: nowrap;
}

.custom-toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* ============================================================
   CARD STAGE
   ============================================================ */
.stage-container {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2.5rem;
  position: relative;
}

/* ---- Prev / Next Navigation Buttons ---- */
.stage-nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  /* Liquid Glass */
  background: var(--glass-white);
  backdrop-filter: blur(32px) saturate(200%);
  -webkit-backdrop-filter: blur(32px) saturate(200%);
  border: var(--border-glass);
  box-shadow: var(--shadow-btn);
  color: var(--text-muted);
  width: 46px;
  height: 46px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: var(--transition-spring);
  z-index: 5;
}

.stage-nav-btn:hover {
  background: rgba(255, 255, 255, 0.92);
  border-color: rgba(255, 255, 255, 1);
  box-shadow: var(--shadow-btn-hover);
  color: var(--accent-color);
  transform: translateY(-50%) scale(1.1);
}

.stage-nav-btn:active {
  transform: translateY(-50%) scale(0.94);
  box-shadow: var(--shadow-btn-pressed);
}

.stage-nav-btn.left { left: 1.5rem; }
.stage-nav-btn.right { right: 1.5rem; }

/* ============================================================
   WORD CARD  — Premium Liquid Glass
   ============================================================ */
.word-card {
  /* Deep liquid glass */
  background: var(--glass-white);
  backdrop-filter: var(--glass-blur-heavy);
  -webkit-backdrop-filter: var(--glass-blur-heavy);
  border-radius: var(--radius-xl);
  width: 100%;
  max-width: 580px;
  min-height: 400px;
  display: flex;
  flex-direction: column;
  padding: 2rem 2.25rem;
  position: relative;
  transition: var(--transition);
  /* Multi-layer shadow for depth */
  box-shadow: var(--shadow-card);
  /* Light-catching top edge */
  border: 1px solid rgba(255, 255, 255, 0.9);
  /* Subtle bottom outer edge */
  outline: 1px solid rgba(150, 160, 180, 0.15);
  outline-offset: 0px;
}

/* Inner top specular highlight */
.word-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 10%;
  right: 10%;
  height: 1px;
  background: linear-gradient(90deg,
    transparent,
    rgba(255,255,255,0.9) 30%,
    rgba(255,255,255,1) 50%,
    rgba(255,255,255,0.9) 70%,
    transparent
  );
  border-radius: var(--radius-pill);
}

.word-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  min-height: 24px;
}

/* ---- Example Sentence Box (glass inset) ---- */
.example-box {
  background: rgba(0, 0, 0, 0.025);
  border: 1px solid rgba(0, 0, 0, 0.06);
  padding: 0.9rem 1.1rem;
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
  display: none;
  position: relative;
  overflow: hidden;
}

.example-box::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: rgba(255,255,255,0.7);
}

.example-title {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-tertiary);
  letter-spacing: 0.8px;
  margin-bottom: 0.4rem;
}

.example-en {
  font-size: 0.9rem;
  color: var(--text-main);
  line-height: 1.5;
  font-weight: 500;
  margin-bottom: 0.3rem;
}

.example-zh {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.45;
}

/* ---- Card Star Button ---- */
.card-star-action-btn {
  background: var(--glass-white-thin);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: var(--border-glass);
  box-shadow: var(--shadow-btn);
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  transition: var(--transition-spring);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: var(--radius-pill);
}

.card-star-action-btn:hover {
  background: rgba(255, 255, 255, 0.85);
  box-shadow: var(--shadow-btn-hover);
  color: #f59e0b;
  transform: scale(1.12);
}

.card-star-action-btn.starred {
  color: #f59e0b;
  background: rgba(245, 158, 11, 0.1);
  border-color: rgba(245, 158, 11, 0.3);
  box-shadow: 0 0 12px rgba(245,158,11,0.2), var(--shadow-btn);
  animation: star-pop 0.35s var(--ease-spring);
}

/* ---- Word Display ---- */
.word-display {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

.word-title {
  font-size: 2.8rem;
  font-weight: 800;
  color: var(--text-main);
  letter-spacing: -1px;
  word-break: break-word;
  line-height: 1.05;
}

.phonetic-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.phonetic-text {
  font-size: 1.1rem;
  color: var(--text-muted);
  font-weight: 400;
  letter-spacing: 0.5px;
}

/* ---- Speak Audio Button ---- */
.speak-btn {
  /* Liquid glass pill button */
  background: var(--glass-white-mid);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: var(--border-glass);
  box-shadow: var(--shadow-btn);
  color: var(--accent-color);
  width: 34px;
  height: 34px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  transition: var(--transition-spring);
}

.speak-btn:hover {
  background: rgba(255, 255, 255, 0.92);
  box-shadow: var(--shadow-btn-hover), 0 0 16px var(--accent-glow);
  transform: scale(1.1);
}

.speak-btn:active {
  transform: scale(0.94);
  box-shadow: var(--shadow-btn-pressed);
}

/* ---- Divider ---- */
.divider {
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(0,0,0,0.07) 30%, rgba(0,0,0,0.07) 70%, transparent);
  width: 100%;
  margin-bottom: 1.25rem;
}

/* ---- Translation Row ---- */
.word-translation-section {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  margin-bottom: 1.5rem;
}

.translation-row {
  font-size: 1.3rem;
  font-weight: 500;
  color: var(--text-main);
  line-height: 1.4;
}

.part-of-speech {
  font-style: italic;
  font-weight: 600;
  color: var(--text-tertiary);
  margin-right: 0.45rem;
  font-size: 0.9em;
}

/* ---- Mnemonic Box ---- */
.mnemonic-box {
  background: linear-gradient(135deg, rgba(0, 113, 227, 0.06), rgba(88, 86, 214, 0.06));
  border: 1px solid rgba(0, 113, 227, 0.12);
  border-left: 3px solid var(--accent-color);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin-top: auto;
  position: relative;
  overflow: hidden;
}

.mnemonic-box::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: rgba(255,255,255,0.6);
}

.mnemonic-title {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--accent-color);
  letter-spacing: 0.8px;
  margin-bottom: 0.35rem;
  opacity: 0.8;
}

.mnemonic-text {
  font-size: 0.9rem;
  line-height: 1.55;
  color: #1a3a5c;
  font-weight: 400;
}

/* ============================================================
   LIST / TABLE MODE
   ============================================================ */
.list-container {
  flex: 1;
  margin: 1.75rem 2rem;
  display: flex;
  flex-direction: column;
  min-height: 0;
  position: relative;
  
  /* Liquid Glass card */
  background: var(--glass-white);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid rgba(255, 255, 255, 0.85);
  outline: 1px solid rgba(150, 160, 180, 0.12);
  outline-offset: 0;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.table-wrapper {
  overflow-x: auto;
  overflow-y: auto;
  width: 100%;
  flex: 1;
  min-height: 0;
  background: transparent;
}

.vocab-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.9rem;
}

.vocab-table th,
.vocab-table td {
  padding: 0.9rem 1.1rem;
  border-bottom: 1px solid rgba(0,0,0,0.05);
  vertical-align: middle;
}

.vocab-table th {
  background: rgba(255, 255, 255, 0.95);
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid rgba(0,0,0,0.06);
}

.vocab-table tr:last-child td { border-bottom: none; }

.vocab-table tbody tr td {
  transition: background-color 0.15s ease;
}

.vocab-table tbody tr:hover td {
  background: rgba(0, 113, 227, 0.04);
}

.table-word {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-main);
  cursor: pointer;
  transition: color 0.15s ease;
}

.table-word:hover {
  color: var(--accent-color);
  text-decoration: underline;
}

.table-ipa-row {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.table-pos {
  font-style: italic;
  font-weight: 600;
  color: var(--text-tertiary);
  font-size: 0.8rem;
}

.table-meaning {
  font-weight: 500;
  color: var(--text-main);
}

.table-mnemonic {
  font-size: 0.82rem;
  color: #1a3a5c;
  line-height: 1.45;
  background: linear-gradient(135deg, rgba(0,113,227,0.06), rgba(88,86,214,0.04));
  padding: 0.45rem 0.75rem;
  border-radius: var(--radius-sm);
  border-left: 2px solid rgba(0,113,227,0.35);
}

/* ============================================================
   TOGGLE CONTROLS (bottom of sidebar)
   ============================================================ */
.toggle-control {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
  cursor: pointer;
  user-select: none;
  width: 100%;
  justify-content: center;
}

.toggle-switch {
  position: relative;
  display: inline-block;
  width: 38px;
  height: 22px;
  flex-shrink: 0;
}

.toggle-switch input { opacity: 0; width: 0; height: 0; }

.slider {
  position: absolute;
  cursor: pointer;
  inset: 0;
  background: rgba(0,0,0,0.14);
  transition: 0.3s var(--ease-smooth);
  border-radius: 22px;
}

.slider:before {
  position: absolute;
  content: '';
  height: 16px;
  width: 16px;
  left: 3px;
  bottom: 3px;
  background: white;
  box-shadow: 0 1px 4px rgba(0,0,0,0.2);
  transition: 0.3s var(--ease-spring);
  border-radius: 50%;
}

input:checked + .slider { background: var(--accent-color); }
input:checked + .slider:before { transform: translateX(16px); }

/* ============================================================
   ANIMATIONS
   ============================================================ */
@keyframes star-pop {
  0%   { transform: scale(1); }
  40%  { transform: scale(1.35) rotate(-8deg); }
  70%  { transform: scale(0.9) rotate(4deg); }
  100% { transform: scale(1) rotate(0); }
}

@keyframes card-enter {
  from { opacity: 0; transform: translateY(10px) scale(0.98); }
  to   { opacity: 1; transform: translateY(0) scale(1); }
}

.word-card {
  animation: card-enter 0.35s var(--ease-out);
}

/* ============================================================
   GRID MODE FOR ALL VOCABULARY LIST (2-Column Dict Layout)
   ============================================================ */
.vocab-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem 3rem;
  padding: 1.5rem;
  width: 100%;
}

.vocab-grid-item {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  padding: 0.8rem 1.2rem;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.45);
  border: 1px solid rgba(255, 255, 255, 0.65);
  transition: var(--transition-spring);
  cursor: pointer;
}

.vocab-grid-item:hover {
  background: rgba(255, 255, 255, 0.85);
  border-color: rgba(0, 113, 227, 0.25);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.vocab-grid-item:active {
  transform: translateY(0);
}

.grid-word {
  font-weight: 700;
  color: var(--text-main);
  font-size: 0.95rem;
  width: 150px;
  flex-shrink: 0;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.grid-pos {
  font-style: italic;
  font-weight: 600;
  color: var(--text-tertiary);
  font-size: 0.8rem;
  width: 32px;
  flex-shrink: 0;
  text-align: left;
}

.grid-meaning {
  font-weight: 500;
  color: var(--text-main);
  font-size: 0.875rem;
  flex: 1;
  text-align: left;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ============================================================
   RESPONSIVE / MOBILE
   ============================================================ */
@media (max-width: 768px) {
  .app-wrapper { flex-direction: column; }

  .sidebar {
    width: 100%;
    height: auto;
    border-right: none;
    border-bottom: var(--border-divider);
  }

  .sidebar-header { padding: 0.75rem 1rem; }
  .sidebar-logo { font-size: 1.3rem; }

  .unit-list {
    flex-direction: row;
    overflow-x: auto;
    overflow-y: hidden;
    padding: 0.4rem 0.75rem;
    gap: 0.4rem;
    height: 56px;
  }

  .unit-item {
    width: auto;
    flex-shrink: 0;
    padding: 0.35rem 0.75rem;
  }

  .unit-item-info {
    max-width: 100%;
    flex-direction: row;
    align-items: center;
    gap: 0.4rem;
  }

  .unit-item-desc { display: none; }

  .sidebar-back-header {
    padding: 0.35rem 0.75rem;
    border-bottom: none;
    font-size: 0.82rem;
    width: auto;
    flex-shrink: 0;
    border-radius: var(--radius-sm);
    background: var(--accent-light);
  }

  .toc-word-item { display: none; }
  .sidebar-settings { display: none; }

  .main-header { padding: 0.65rem 1rem; }

  .mode-btn span { display: none; }
  .mode-btn { padding: 0.35rem 0.7rem; }

  .stage-nav-btn { display: none; }
  .stage-container {
    padding: 1.5rem 1rem 8.5rem !important;
    overflow-y: auto !important;
    box-sizing: border-box !important;
    min-height: calc(100vh - 60px) !important;
  }
  .stage-container:not([style*="display: none"]) {
    display: flex !important;
    flex-direction: column !important;
    align-items: center !important;
    justify-content: flex-start !important;
  }

  .word-card {
    padding: 1.25rem 1.25rem 1.5rem;
    min-height: 340px;
    border-radius: var(--radius-lg);
  }

  .word-title { font-size: 2.2rem; }

  .list-container {
    margin: 0.5rem;
    padding: 0;
    border-radius: var(--radius-md);
  }

  .vocab-table th,
  .vocab-table td { padding: 0.55rem 0.5rem; font-size: 0.78rem; }

  .table-mnemonic { padding: 0.35rem 0.55rem; font-size: 0.74rem; }

  .table-wrapper { border-radius: 0; }

  /* Mobile override for 2-column vocabulary grid */
  .vocab-grid {
    grid-template-columns: 1fr;
    gap: 0.5rem;
    padding: 0.75rem;
  }

  .vocab-grid-item {
    padding: 0.65rem 0.9rem;
  }

  .grid-word {
    width: 120px;
  }

  #add-to-desktop-btn .btn-text {
    display: none;
  }
}

/* ============================================================
   HOME SCREEN GUIDE MODAL (Liquid Glass)
   ============================================================ */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.3s ease;
  padding: 1.5rem;
}

.modal-overlay.show {
  opacity: 1;
}

.modal-card {
  background: var(--glass-surface);
  backdrop-filter: var(--glass-blur-heavy);
  -webkit-backdrop-filter: var(--glass-blur-heavy);
  border: 1px solid rgba(255, 255, 255, 0.85);
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.2);
  border-radius: var(--radius-lg);
  padding: 2.25rem 2rem;
  max-width: 420px;
  width: 100%;
  transform: scale(0.9) translateY(20px);
  transition: transform 0.35s var(--ease-spring);
  text-align: center;
  position: relative;
}

.modal-overlay.show .modal-card {
  transform: scale(1) translateY(0);
}

.modal-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.75rem;
  letter-spacing: -0.2px;
}

.modal-desc {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 1.5rem;
}

.guide-steps {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  text-align: left;
  margin-bottom: 1.75rem;
  background: rgba(0, 0, 0, 0.03);
  padding: 1.1rem;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(0, 0, 0, 0.05);
}

.guide-step-item {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  font-size: 0.88rem;
  line-height: 1.5;
  color: var(--text-main);
}

.guide-step-num {
  background: var(--accent-color);
  color: white;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 700;
  flex-shrink: 0;
  margin-top: 1px;
}

.modal-close-btn {
  background: var(--accent-color);
  color: white;
  border: none;
  border-radius: var(--radius-pill);
  padding: 0.65rem 2rem;
  font-size: 0.88rem;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0, 113, 227, 0.35);
  transition: var(--transition-spring);
  width: 100%;
}

.modal-close-btn:hover {
  background: var(--accent-vivid);
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(0, 113, 227, 0.45);
}

.modal-close-btn:active {
  transform: translateY(0);
}

/* ============================================================
   MOBILE-ONLY UTILITIES
   ============================================================ */
.mobile-only {
  display: none !important;
}

/* ============================================================
   MOBILE ZEN EXPERIENCE EXTENSIONS (max-width: 768px)
   ============================================================ */
@media (max-width: 768px) {
  /* Helper to hide desktop elements */
  .mobile-only {
    display: block !important;
  }
  #mobile-control-bar.mobile-only {
    display: flex !important;
  }
  #mobile-back-to-grid-btn.mobile-only,
  #mobile-toggle-drawer-btn.mobile-only {
    display: flex !important;
  }

  #add-to-desktop-btn,
  .view-mode-selector {
    display: none !important;
  }

  #filter-star-btn {
    display: flex !important;
    background: transparent !important;
    border: none !important;
    box-shadow: none !important;
    color: var(--accent-color) !important;
    width: 38px;
    height: 38px;
    border-radius: 50%;
    align-items: center;
    justify-content: center;
    font-size: 1.15rem !important;
    padding: 0 !important;
    transition: var(--transition-spring);
  }
  #filter-star-btn:active {
    background: var(--accent-light) !important;
    transform: scale(0.9);
  }
  #filter-star-btn.starred-active {
    color: #f59e0b !important;
  }

  /* 1. Mobile Splash Welcome Screen */
  #splash-screen {
    position: fixed;
    inset: 0;
    z-index: 99999;
    background: #e8eaf0;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 1;
    visibility: visible;
    transition: opacity 0.6s cubic-bezier(0.25, 1, 0.5, 1), visibility 0.6s;
  }
  #splash-screen::after {
    content: '';
    position: absolute;
    inset: 0;
    z-index: -1;
    background:
      radial-gradient(ellipse 80% 60% at 10% 20%, rgba(174, 210, 255, 0.75), transparent),
      radial-gradient(ellipse 60% 80% at 90% 80%, rgba(213, 190, 255, 0.65), transparent),
      radial-gradient(ellipse 70% 50% at 50% 100%, rgba(255, 200, 220, 0.5), transparent),
      radial-gradient(ellipse 50% 60% at 80% 10%, rgba(180, 230, 250, 0.6), transparent);
  }
  #splash-screen.fade-out {
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
  }
  .splash-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    z-index: 10;
    width: 100%;
    max-width: 320px;
  }
  .splash-logo {
    width: 110px;
    height: 110px;
    border-radius: 26px;
    box-shadow: 0 12px 36px rgba(0, 113, 227, 0.25);
    margin-bottom: 1.5rem;
    animation: splash-pop 1.2s var(--ease-spring) forwards;
  }
  .splash-title {
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--text-main);
    margin-bottom: 0.3rem;
    letter-spacing: -0.5px;
  }
  .splash-subtitle {
    font-size: 0.88rem;
    color: var(--text-muted);
    letter-spacing: 0.5px;
    margin-bottom: 2rem;
  }
  .splash-loader {
    width: 140px;
    height: 3px;
    background: rgba(0,0,0,0.06);
    border-radius: 9px;
    overflow: hidden;
  }
  .splash-loader-bar {
    width: 0%;
    height: 100%;
    background: var(--accent-color);
    border-radius: 9px;
    animation: load-progress 1.5s cubic-bezier(0.1, 0.8, 0.2, 1) forwards;
  }
  @keyframes load-progress {
    to { width: 100%; }
  }
  @keyframes splash-pop {
    from { transform: scale(0.7) translateY(10px); opacity: 0; }
    to { transform: scale(1) translateY(0); opacity: 1; }
  }

  /* 2. Mobile Unit Selection Grid Screen */
  #mobile-unit-select-screen {
    position: fixed;
    inset: 0;
    z-index: 8000;
    background: #e8eaf0;
    overflow-y: auto;
    padding: 2.5rem 1.25rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.4s ease;
  }
  #mobile-unit-select-screen::after {
    content: '';
    position: fixed !important;
    inset: 0;
    z-index: -1;
    background:
      radial-gradient(ellipse 80% 60% at 10% 20%, rgba(174, 210, 255, 0.75), transparent),
      radial-gradient(ellipse 60% 80% at 90% 80%, rgba(213, 190, 255, 0.65), transparent),
      radial-gradient(ellipse 70% 50% at 50% 100%, rgba(255, 200, 220, 0.5), transparent),
      radial-gradient(ellipse 50% 60% at 80% 10%, rgba(180, 230, 250, 0.6), transparent);
  }
  #mobile-unit-select-screen:not(.slide-out) ~ .app-wrapper #mobile-control-bar {
    display: none !important;
  }
  #mobile-unit-select-screen.slide-out {
    transform: translateY(100vh);
    opacity: 0;
    pointer-events: none;
  }
  .grid-screen-header {
    padding-bottom: 0.5rem;
    border-bottom: 1px solid rgba(0,0,0,0.06);
    z-index: 10;
  }
  .grid-title {
    font-size: 1.8rem;
    font-weight: 800;
    color: var(--text-main);
  }
  .grid-desc {
    font-size: 0.85rem;
    color: var(--text-muted);
  }
  .grid-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.8rem;
    padding-bottom: 3rem;
    z-index: 10;
  }
  .grid-unit-card {
    background: rgba(255, 255, 255, 0.58) !important;
    backdrop-filter: blur(20px) !important;
    -webkit-backdrop-filter: blur(20px) !important;
    border: 1px solid rgba(255, 255, 255, 0.8) !important;
    border-radius: var(--radius-md) !important;
    padding: 1rem 0.9rem !important;
    display: flex !important;
    flex-direction: column !important;
    justify-content: space-between !important;
    gap: 0.4rem !important;
    text-align: left !important;
    cursor: pointer !important;
    transition: var(--transition-spring) !important;
    box-shadow: 
      0 4px 12px rgba(0, 0, 0, 0.03),
      inset 0 1px 0 rgba(255,255,255,0.9) !important;
    min-height: 110px !important;
    position: relative !important;
  }
  .grid-unit-card:active {
    transform: scale(0.96) translateY(2px) !important;
    background: rgba(255, 255, 255, 0.78) !important;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.02) !important;
  }
  .grid-unit-card-badge {
    font-size: 0.65rem;
    font-weight: 700;
    color: var(--accent-color);
    text-transform: uppercase;
    background: rgba(0, 113, 227, 0.08);
    padding: 2px 8px;
    border-radius: var(--radius-pill);
    width: fit-content;
    letter-spacing: 0.5px;
  }
  .grid-unit-card-badge.all {
    color: #5856d6;
    background: rgba(88, 86, 214, 0.08);
  }
  .grid-unit-card-name {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-main);
    line-height: 1.35;
    overflow: hidden;
    text-overflow: ellipsis;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    min-height: 38px;
  }
  .grid-unit-card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 0.2rem;
  }
  .grid-unit-card-count {
    font-size: 0.72rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 4px;
  }
  .grid-unit-card-arrow {
    font-size: 0.7rem;
    color: var(--text-tertiary);
    transition: transform 0.28s var(--ease-spring);
  }
  .grid-unit-card:active .grid-unit-card-arrow {
    transform: translateX(2px);
    color: var(--accent-color);
  }

  /* 3. Collapsible Word Directory Drawer */
  .sidebar {
    position: fixed !important;
    left: -300px !important;
    top: 0 !important;
    bottom: 0 !important;
    width: 280px !important;
    height: 100vh !important;
    z-index: 12000 !important;
    box-shadow: 10px 0 30px rgba(0,0,0,0.15) !important;
    transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1) !important;
    border-right: 1px solid rgba(255,255,255,0.4) !important;
  }
  .sidebar.open {
    transform: translateX(300px) !important;
  }
  .unit-list {
    flex-direction: column !important;
    overflow-y: auto !important;
    overflow-x: hidden !important;
    height: 100% !important;
    padding: 0.75rem !important;
    gap: 0.25rem !important;
  }
  .toc-word-item {
    display: flex !important;
  }

  /* Header icon buttons styles */
  .header-icon-btn {
    background: transparent;
    border: none;
    color: var(--accent-color);
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.15rem;
    cursor: pointer;
    transition: var(--transition-spring);
  }
  .header-icon-btn:active {
    background: var(--accent-light);
    transform: scale(0.9);
  }

  /* 4. Word Card Customization: Borderless simplified word layout */
  .word-card {
    background: transparent !important;
    border: none !important;
    outline: none !important;
    box-shadow: none !important;
    padding: 0.5rem !important;
    margin: auto 0 !important; /* Centered vertically and horizontally! */
    width: 100% !important;
    max-width: 100% !important;
    min-height: auto !important;
    display: flex !important;
    flex-direction: column !important;
    align-items: center !important;
    text-align: center !important;
    position: relative !important;
  }
  .word-card-fraction {
    position: absolute !important;
    top: -0.5rem !important;
    left: 0.5rem !important;
    font-size: 0.8rem !important;
    color: var(--text-tertiary) !important;
    font-weight: 500 !important;
    background: rgba(0, 0, 0, 0.04) !important;
    padding: 0.2rem 0.6rem !important;
    border-radius: var(--radius-pill) !important;
    letter-spacing: 0.3px !important;
    pointer-events: none !important;
  }
  .word-card::before {
    display: none !important; /* Hide Apple line reflection */
  }
  .word-card-header {
    display: none !important; /* Hide header controls */
  }
  .word-display {
    align-items: center !important;
    gap: 0.5rem !important;
    margin-top: 0.2rem !important;
  }
  .word-title {
    font-size: 2.8rem !important;
    font-weight: 700 !important;
    letter-spacing: -1px !important;
    background: linear-gradient(135deg, var(--text-main), #007aff) !important;
    -webkit-background-clip: text !important;
    -webkit-text-fill-color: transparent !important;
    line-height: 1.15 !important;
    text-shadow: 0 4px 12px rgba(0,0,0,0.01) !important;
  }
  .phonetic-row {
    justify-content: center !important;
  }
  .phonetic-text {
    font-size: 1.15rem !important;
  }
  .speak-btn {
    display: none !important; /* Hidden in mobile as clicking spelling pronounces word */
  }
  .divider {
    display: none !important; /* Remove card divider line */
  }
  .word-translation-section {
    margin-top: 1.5rem !important;
    margin-bottom: 2rem !important;
  }
  .translation-row {
    font-size: 1.5rem !important;
    font-weight: 600 !important;
    color: #1a3a5c !important;
    text-align: center !important;
  }
  .part-of-speech {
    font-size: 1.25rem !important;
    color: var(--accent-color) !important;
    margin-right: 0.5rem !important;
  }

  /* 5. Collapsible details (example sentences and memory) */
  .example-box,
  .mnemonic-box {
    display: none !important;
    width: 100% !important;
    max-width: 480px !important;
    margin: 0.5rem 0 !important;
    border-radius: var(--radius-md) !important;
    box-shadow: var(--shadow-sm) !important;
    opacity: 0;
    transform: translateY(15px);
    transition: opacity 0.35s ease, transform 0.35s var(--ease-spring);
  }
  
  .word-card.show-details .example-box,
  .word-card.show-details .mnemonic-box {
    display: block !important;
    opacity: 1 !important;
    transform: translateY(0) !important;
  }

  .example-box {
    background: rgba(255, 255, 255, 0.45) !important;
    backdrop-filter: blur(20px) !important;
    -webkit-backdrop-filter: blur(20px) !important;
    border: 1px solid rgba(255,255,255,0.7) !important;
  }
  .mnemonic-box {
    background: rgba(255, 255, 255, 0.35) !important;
    backdrop-filter: blur(20px) !important;
    -webkit-backdrop-filter: blur(20px) !important;
    border: 1px solid rgba(255,255,255,0.5) !important;
    border-left: 3px solid var(--accent-color) !important;
  }

  /* 6. Mobile bottom navigation capsule bar */
  #mobile-control-bar {
    position: fixed !important;
    bottom: 2.2rem;
    left: 50%;
    transform: translateX(-50%);
    z-index: 9999;
    display: flex !important;
    align-items: center;
    justify-content: space-around;
    gap: 1.25rem;
    padding: 0.55rem 1.6rem;
    background: rgba(255, 255, 255, 0.45);
    backdrop-filter: blur(24px) saturate(180%);
    -webkit-backdrop-filter: blur(24px) saturate(180%);
    border-radius: 999px;
    border: 1px solid rgba(255, 255, 255, 0.7);
    box-shadow: 
      0 4px 12px rgba(0, 0, 0, 0.05),
      0 16px 36px rgba(0, 0, 0, 0.08),
      inset 0 1px 0 rgba(255,255,255,0.7);
    width: auto;
    min-width: 280px;
    max-width: 90%;
  }
  .mobile-ctrl-btn {
    background: transparent;
    border: none;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.15rem;
    color: var(--text-main);
    cursor: pointer;
    transition: var(--transition-spring);
  }
  .mobile-ctrl-btn:active {
    transform: scale(0.85);
    background: rgba(255, 255, 255, 0.2);
  }
  .mobile-ctrl-btn.starred {
    color: #f59e0b !important;
    animation: star-pop 0.35s var(--ease-spring);
  }
  .mobile-ctrl-btn.active {
    color: var(--accent-color) !important;
    background: rgba(0, 113, 227, 0.08);
    box-shadow: inset 0 1px 2px rgba(0,0,0,0.05);
  }
}