/* ============================================
   GRE Vocab Mastery — Style System
   ============================================ */

/* ---------- CSS Custom Properties ---------- */
:root {
  /* Midnight theme (default) */
  --bg-primary: #0f0c29;
  --bg-secondary: #1a1640;
  --bg-tertiary: #252054;
  --surface: rgba(255, 255, 255, 0.04);
  --surface-hover: rgba(255, 255, 255, 0.08);
  --surface-active: rgba(255, 255, 255, 0.12);
  --glass: rgba(255, 255, 255, 0.06);
  --glass-border: rgba(255, 255, 255, 0.1);
  --text-primary: #f0eef6;
  --text-secondary: rgba(240, 238, 246, 0.7);
  --text-muted: rgba(240, 238, 246, 0.4);
  --accent: #6c63ff;
  --accent-glow: rgba(108, 99, 255, 0.3);
  --accent-soft: rgba(108, 99, 255, 0.15);
  --correct: #34d399;
  --correct-bg: rgba(52, 211, 153, 0.12);
  --wrong: #f87171;
  --wrong-bg: rgba(248, 113, 113, 0.12);
  --warning: #fbbf24;
  --warning-bg: rgba(251, 191, 36, 0.12);
  --card-accent: var(--accent);
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.2);
  --shadow-md: 0 8px 32px rgba(0,0,0,0.3);
  --shadow-lg: 0 16px 48px rgba(0,0,0,0.4);
  --shadow-glow: 0 0 40px var(--accent-glow);
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --transition-fast: 0.15s ease;
  --transition-base: 0.25s ease;
  --transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---------- Theme Variants ---------- */
[data-theme="aurora"] {
  --bg-primary: #0d1b2a;
  --bg-secondary: #1b2838;
  --bg-tertiary: #2a4a5e;
  --accent: #64ffda;
  --accent-glow: rgba(100, 255, 218, 0.25);
  --accent-soft: rgba(100, 255, 218, 0.12);
}
[data-theme="forest"] {
  --bg-primary: #0b1a0b;
  --bg-secondary: #1a2f1a;
  --bg-tertiary: #2d4a2d;
  --accent: #86efac;
  --accent-glow: rgba(134, 239, 172, 0.25);
  --accent-soft: rgba(134, 239, 172, 0.12);
}
[data-theme="sunset"] {
  --bg-primary: #1a0a0a;
  --bg-secondary: #2d1515;
  --bg-tertiary: #4a2020;
  --accent: #fb923c;
  --accent-glow: rgba(251, 146, 60, 0.25);
  --accent-soft: rgba(251, 146, 60, 0.12);
}
[data-theme="ocean"] {
  --bg-primary: #0a1628;
  --bg-secondary: #122240;
  --bg-tertiary: #1a3358;
  --accent: #38bdf8;
  --accent-glow: rgba(56, 189, 248, 0.25);
  --accent-soft: rgba(56, 189, 248, 0.12);
}
[data-theme="rose"] {
  --bg-primary: #1a0f18;
  --bg-secondary: #2d1a28;
  --bg-tertiary: #4a2a42;
  --accent: #f472b6;
  --accent-glow: rgba(244, 114, 182, 0.25);
  --accent-soft: rgba(244, 114, 182, 0.12);
}

/* ---------- Reset & Base ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Animated background gradient */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background:
    radial-gradient(ellipse at 20% 20%, var(--accent-glow) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 80%, rgba(139, 92, 246, 0.1) 0%, transparent 50%);
  pointer-events: none;
  z-index: 0;
  animation: bgPulse 8s ease-in-out infinite alternate;
}
@keyframes bgPulse {
  0% { opacity: 0.6; }
  100% { opacity: 1; }
}

/* ---------- Top Bar ---------- */
#top-bar {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(20px) saturate(1.4);
  -webkit-backdrop-filter: blur(20px) saturate(1.4);
  background: rgba(15, 12, 41, 0.75);
  border-bottom: 1px solid var(--glass-border);
}
.top-bar-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  gap: 16px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}
.logo-icon { font-size: 1.5rem; }
.logo-text {
  font-weight: 800;
  font-size: 1.15rem;
  background: linear-gradient(135deg, var(--text-primary), var(--accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.02em;
}

/* ---------- Mode Tabs ---------- */
.mode-tabs {
  display: flex;
  gap: 4px;
  background: var(--surface);
  border-radius: var(--radius-md);
  padding: 3px;
  border: 1px solid var(--glass-border);
  flex-shrink: 0;
}
.mode-tab {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: none;
  border-radius: calc(var(--radius-md) - 3px);
  background: transparent;
  color: var(--text-muted);
  font-family: var(--font-sans);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}
.mode-tab:hover {
  color: var(--text-secondary);
  background: var(--surface);
}
.mode-tab.active {
  background: linear-gradient(135deg, var(--accent), color-mix(in srgb, var(--accent) 70%, white));
  color: #fff;
  box-shadow: 0 2px 12px var(--accent-glow);
}
.mode-tab svg { flex-shrink: 0; }

/* ---------- Stats Row ---------- */
.stats-row {
  display: flex;
  gap: 8px;
  flex: 1;
  justify-content: center;
  flex-wrap: wrap;
}
.stat-chip {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  background: var(--surface);
  border: 1px solid var(--glass-border);
  font-size: 0.8rem;
  white-space: nowrap;
  transition: background var(--transition-fast);
}
.stat-chip:hover { background: var(--surface-hover); }
.stat-icon { font-size: 0.9rem; }
.stat-value { font-weight: 700; color: var(--accent); font-family: var(--font-mono); font-size: 0.85rem; }
.stat-label { color: var(--text-muted); font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.05em; }

.icon-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--glass-border);
  background: var(--surface);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}
.icon-btn:hover { background: var(--surface-hover); color: var(--text-primary); }

/* ---------- Settings Panel ---------- */
.settings-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
}
.settings-overlay.active { opacity: 1; pointer-events: all; }

.settings-panel {
  position: fixed;
  top: 0;
  right: 0;
  width: 380px;
  max-width: 90vw;
  height: 100vh;
  background: var(--bg-secondary);
  border-left: 1px solid var(--glass-border);
  z-index: 201;
  transform: translateX(100%);
  transition: transform var(--transition-slow);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}
.settings-panel.active { transform: translateX(0); }
.settings-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 24px;
  border-bottom: 1px solid var(--glass-border);
}
.settings-header h2 { font-size: 1.2rem; font-weight: 700; }
.settings-body { padding: 24px; flex: 1; overflow-y: auto; }
.settings-section { margin-bottom: 28px; }
.settings-section h3 {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 12px;
  font-weight: 600;
}

/* Theme Swatches */
.theme-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}
.theme-swatch {
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  padding: 4px;
  background: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}
.theme-swatch.active { border-color: var(--accent); }
.theme-swatch:hover { border-color: var(--text-muted); }
.swatch-color {
  width: 100%;
  height: 36px;
  border-radius: var(--radius-sm);
  display: block;
}
.swatch-label { font-size: 0.65rem; color: var(--text-secondary); font-weight: 500; }

/* Color Picker */
.color-picker-row {
  display: flex;
  align-items: center;
  gap: 12px;
}
#card-color-picker {
  width: 44px;
  height: 36px;
  border: 2px solid var(--glass-border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  cursor: pointer;
  padding: 2px;
}
#card-color-picker::-webkit-color-swatch-wrapper { padding: 0; }
#card-color-picker::-webkit-color-swatch { border: none; border-radius: 4px; }
.color-label { font-family: var(--font-mono); font-size: 0.8rem; color: var(--text-secondary); }
.btn-small {
  padding: 6px 12px;
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: 0.7rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-small:hover { background: var(--surface-hover); color: var(--text-primary); }

/* Group Filter */
.group-filter {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  max-height: 180px;
  overflow-y: auto;
  padding-right: 4px;
}
.group-filter::-webkit-scrollbar { width: 4px; }
.group-filter::-webkit-scrollbar-thumb { background: var(--glass-border); border-radius: 2px; }
.group-btn {
  padding: 5px 10px;
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: 0.72rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
  font-weight: 500;
}
.group-btn:hover { background: var(--surface-hover); color: var(--text-primary); }
.group-btn.active {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
}

/* Danger Button */
.btn-danger {
  padding: 10px 20px;
  border: 1px solid var(--wrong);
  border-radius: var(--radius-sm);
  background: var(--wrong-bg);
  color: var(--wrong);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
  width: 100%;
}
.btn-danger:hover { background: rgba(248, 113, 113, 0.25); }

/* ---------- Mode Containers ---------- */
.mode-container {
  position: relative;
  z-index: 1;
  max-width: 780px;
  margin: 0 auto;
  padding: 24px 20px 40px;
  display: none;
}
.mode-container.active {
  display: block;
  animation: fadeIn 0.3s ease-out;
}
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Quiz mode uses tighter width */
#quiz-mode { max-width: 680px; }

/* ============================================
   STUDY MODE STYLES
   ============================================ */

/* ---------- Section Layout ---------- */
.study-section { margin-bottom: 24px; }
.section-header {
  text-align: center;
  margin-bottom: 28px;
}
.section-title {
  font-size: 1.8rem;
  font-weight: 900;
  letter-spacing: -0.03em;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  margin-bottom: 8px;
}
.section-icon { font-size: 1.5rem; }
.section-subtitle {
  font-size: 0.88rem;
  color: var(--text-secondary);
  max-width: 500px;
  margin: 0 auto;
  line-height: 1.5;
}

/* ---------- Group Grid ---------- */
.group-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 12px;
}
.group-card {
  position: relative;
  padding: 18px 16px;
  border-radius: var(--radius-lg);
  background: linear-gradient(145deg, var(--glass), rgba(255,255,255,0.02));
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  cursor: pointer;
  transition: all var(--transition-base);
  overflow: hidden;
}
.group-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  opacity: 0;
  transition: opacity var(--transition-fast);
}
.group-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  box-shadow: var(--shadow-md), 0 0 20px var(--accent-glow);
}
.group-card:hover::before { opacity: 1; }
.group-card.completed {
  border-color: rgba(52, 211, 153, 0.3);
}
.group-card.completed::before {
  background: linear-gradient(90deg, transparent, var(--correct), transparent);
  opacity: 0.7;
}
.group-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}
.group-card-title {
  font-weight: 800;
  font-size: 0.95rem;
  color: var(--text-primary);
}
.group-card-icon {
  font-size: 1.1rem;
}
.group-card-stats {
  font-size: 0.72rem;
  color: var(--text-muted);
  font-weight: 500;
  margin-bottom: 8px;
}
.group-card-progress {
  width: 100%;
  height: 4px;
  background: var(--surface);
  border-radius: 2px;
  overflow: hidden;
}
.group-card-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 60%, white));
  border-radius: 2px;
  transition: width var(--transition-slow);
}
.group-card.completed .group-card-progress-fill {
  background: linear-gradient(90deg, var(--correct), color-mix(in srgb, var(--correct) 60%, white));
}
.group-card-badges {
  display: flex;
  gap: 6px;
  margin-top: 8px;
}
.group-mini-badge {
  font-size: 0.6rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 2px 8px;
  border-radius: 10px;
  background: var(--accent-soft);
  color: var(--accent);
}
.group-mini-badge.quiz-ready {
  background: var(--correct-bg);
  color: var(--correct);
}
.group-mini-badge.locked {
  background: var(--surface);
  color: var(--text-muted);
}

/* ---------- Study Nav Header ---------- */
.study-nav-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}
.btn-back {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-back:hover { background: var(--surface-hover); color: var(--text-primary); }
.study-group-title {
  font-weight: 800;
  font-size: 1.15rem;
  flex: 1;
}
.study-progress-badge {
  font-size: 0.75rem;
  font-weight: 700;
  padding: 6px 14px;
  border-radius: 20px;
  background: var(--accent-soft);
  color: var(--accent);
  font-family: var(--font-mono);
}
.drill-score {
  background: var(--correct-bg);
  color: var(--correct);
}
.study-progress-track { margin-bottom: 8px; }

/* ---------- Study Card ---------- */
.study-card {
  border-radius: var(--radius-xl);
  background: linear-gradient(145deg, var(--glass), rgba(255,255,255,0.02));
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  overflow: hidden;
  box-shadow: var(--shadow-md), var(--shadow-glow);
  margin-bottom: 20px;
  animation: cardSlideIn 0.35s ease-out;
}
@keyframes cardSlideIn {
  from { opacity: 0; transform: translateX(20px); }
  to { opacity: 1; transform: translateX(0); }
}
.study-card-header {
  padding: 28px 28px 0;
  border-bottom: 1px solid var(--glass-border);
  padding-bottom: 20px;
  position: relative;
}
.study-card-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, transparent, var(--card-accent), transparent);
}
.study-word-row {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 10px;
}
.study-word {
  font-size: 2.6rem;
  font-weight: 900;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--text-primary), var(--card-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.1;
}
.audio-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 2px solid var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  cursor: pointer;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}
.audio-btn:hover {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 0 20px var(--accent-glow);
  transform: scale(1.08);
}
.audio-btn:active { transform: scale(0.95); }
.audio-btn.speaking {
  animation: audioRipple 1s ease-out infinite;
}
@keyframes audioRipple {
  0% { box-shadow: 0 0 0 0 var(--accent-glow); }
  100% { box-shadow: 0 0 0 16px transparent; }
}

.study-meta-row {
  display: flex;
  align-items: center;
  gap: 10px;
}
.study-pos {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 4px 12px;
  border-radius: 6px;
  background: var(--surface);
  color: var(--text-secondary);
  border: 1px solid var(--glass-border);
}
.study-connotation {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 4px 12px;
  border-radius: 20px;
}
.study-connotation[data-connotation="Positive"] { background: var(--correct-bg); color: var(--correct); }
.study-connotation[data-connotation="Negative"] { background: var(--wrong-bg); color: var(--wrong); }
.study-connotation[data-connotation="Neutral"] { background: var(--surface); color: var(--text-secondary); }
.study-connotation[data-connotation="Context-Dependent"] { background: var(--warning-bg); color: var(--warning); }

/* Study Card Body */
.study-card-body {
  padding: 24px 28px 28px;
}
.study-detail-block {
  display: flex;
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px solid rgba(255,255,255,0.04);
}
.study-detail-block:last-of-type { border-bottom: none; }
.detail-icon {
  font-size: 1.15rem;
  flex-shrink: 0;
  width: 24px;
  text-align: center;
  padding-top: 2px;
}
.detail-content { flex: 1; min-width: 0; }
.detail-label {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 4px;
  font-weight: 600;
}
.detail-value {
  font-size: 0.9rem;
  color: var(--text-primary);
  line-height: 1.6;
}
.root-block .detail-value {
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.82rem;
}
.mnemonic-block {
  background: var(--accent-soft);
  border-radius: var(--radius-md);
  padding: 14px 16px !important;
  margin: 6px 0;
  border-bottom: none !important;
}
.mnemonic-block .detail-value {
  font-weight: 600;
  font-style: italic;
}
.study-sentence {
  font-style: italic;
  color: var(--text-secondary);
}
.study-tags-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  padding-top: 14px;
}
.study-tag-group { }
.study-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  margin-top: 6px;
}
.study-tag {
  font-size: 0.72rem;
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 500;
}
.study-tag.antonym {
  background: var(--wrong-bg);
  color: var(--wrong);
}

/* ---------- Study Card Nav ---------- */
.study-card-nav {
  display: flex;
  gap: 10px;
  justify-content: center;
  align-items: center;
  margin-bottom: 16px;
}
.study-card-nav .btn-secondary {
  display: flex;
  align-items: center;
  gap: 6px;
}
.btn-learned {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border: 2px solid var(--glass-border);
  border-radius: var(--radius-md);
  background: var(--surface);
  color: var(--text-secondary);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-learned:hover {
  border-color: var(--correct);
  background: var(--correct-bg);
  color: var(--correct);
}
.btn-learned.active {
  border-color: var(--correct);
  background: var(--correct-bg);
  color: var(--correct);
}
.learned-check {
  font-size: 1.1rem;
  transition: transform var(--transition-fast);
}
.btn-learned.active .learned-check {
  transform: scale(1.2);
}

/* ---------- Study Actions ---------- */
.study-actions {
  display: flex;
  gap: 10px;
  margin-bottom: 20px;
}
.btn-drill {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 20px;
  border: 2px solid var(--accent);
  border-radius: var(--radius-md);
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-drill:hover {
  background: var(--accent);
  color: #fff;
  box-shadow: var(--shadow-glow);
  transform: translateY(-1px);
}
.btn-quiz-launch {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 20px;
  border: none;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--accent), color-mix(in srgb, var(--accent) 70%, white));
  color: #fff;
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-quiz-launch:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-glow);
}
.btn-quiz-launch:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

/* ---------- Audio Player Bar ---------- */
.audio-player-bar {
  background: linear-gradient(145deg, var(--bg-secondary), var(--bg-tertiary));
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  padding: 14px 18px;
  margin-top: 8px;
}
.audio-player-inner {
  display: flex;
  align-items: center;
  gap: 14px;
}
.audio-control-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 2px solid var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  cursor: pointer;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}
.audio-control-btn:hover {
  background: var(--accent);
  color: #fff;
}
.audio-control-btn.playing {
  background: var(--accent);
  color: #fff;
  animation: audioRipple 1.5s ease-out infinite;
}
.audio-info {
  flex: 1;
  min-width: 0;
}
.audio-label {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
  display: block;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.audio-progress-track {
  width: 100%;
  height: 3px;
  background: var(--surface);
  border-radius: 2px;
  overflow: hidden;
}
.audio-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 60%, white));
  border-radius: 2px;
  transition: width 0.3s linear;
}
.audio-controls {
  display: flex;
  gap: 10px;
  flex-shrink: 0;
}
.audio-control-label {
  display: flex;
  flex-direction: column;
  gap: 2px;
  font-size: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-weight: 600;
}
.audio-control-label select {
  padding: 4px 6px;
  border: 1px solid var(--glass-border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  cursor: pointer;
  outline: none;
}
.audio-control-label select:focus {
  border-color: var(--accent);
}

/* ============================================
   MATCHING DRILL STYLES
   ============================================ */

.drill-instructions {
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 20px;
}
.drill-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 20px;
}
.drill-column {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.drill-item {
  padding: 14px 16px;
  border-radius: var(--radius-md);
  border: 2px solid var(--glass-border);
  background: var(--surface);
  color: var(--text-primary);
  font-size: 0.88rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
  user-select: none;
  min-height: 52px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.drill-item:hover:not(.matched):not(.disabled) {
  border-color: var(--accent);
  background: var(--accent-soft);
  transform: translateY(-1px);
}
.drill-item.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
  box-shadow: 0 0 16px var(--accent-glow);
}
.drill-item.matched {
  border-color: var(--correct);
  background: var(--correct-bg);
  color: var(--correct);
  cursor: default;
  opacity: 0.7;
}
.drill-item.wrong-match {
  animation: drillShake 0.5s ease;
  border-color: var(--wrong);
  background: var(--wrong-bg);
}
@keyframes drillShake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-6px); }
  40% { transform: translateX(6px); }
  60% { transform: translateX(-4px); }
  80% { transform: translateX(4px); }
}
.drill-item.disabled {
  cursor: default;
  opacity: 0.3;
}
.drill-def-item {
  font-size: 0.78rem;
  font-weight: 500;
  text-align: left;
  line-height: 1.4;
  min-height: 60px;
}

.drill-feedback {
  text-align: center;
  padding: 16px;
  border-radius: var(--radius-md);
  margin-bottom: 16px;
  animation: slideUp 0.3s ease-out;
}
.drill-feedback.correct-feedback {
  background: var(--correct-bg);
  border: 1px solid rgba(52,211,153,0.3);
}
.drill-feedback.wrong-feedback {
  background: var(--wrong-bg);
  border: 1px solid rgba(248,113,113,0.3);
}
.drill-feedback.complete-feedback {
  background: linear-gradient(135deg, var(--accent-soft), var(--correct-bg));
  border: 1px solid var(--accent);
}
.drill-feedback-icon { font-size: 1.5rem; margin-bottom: 4px; }
.drill-feedback-text { font-size: 0.9rem; font-weight: 700; }

.drill-nav {
  display: flex;
  gap: 10px;
  justify-content: center;
}

/* ============================================
   QUIZ MODE STYLES (preserved from original)
   ============================================ */

/* Progress Bar */
.progress-track {
  width: 100%;
  height: 4px;
  background: var(--surface);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 8px;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), color-mix(in srgb, var(--accent) 60%, white));
  border-radius: 2px;
  transition: width var(--transition-slow);
}
.progress-meta {
  display: flex;
  justify-content: space-between;
  font-size: 0.72rem;
  color: var(--text-muted);
  margin-bottom: 28px;
  font-weight: 500;
}

/* ---------- Flashcard ---------- */
.card-container {
  perspective: 1200px;
  margin-bottom: 28px;
}
.flashcard {
  width: 100%;
  min-height: 320px;
  position: relative;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
  cursor: default;
}
.flashcard.flipped { transform: rotateY(180deg); }
.card-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-xl);
  padding: 36px 32px;
  display: flex;
  flex-direction: column;
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  overflow: hidden;
}
.card-front {
  background: linear-gradient(145deg, var(--glass), rgba(255,255,255,0.02));
  justify-content: center;
  align-items: center;
  text-align: center;
  box-shadow: var(--shadow-md), var(--shadow-glow);
}
.card-front::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, transparent, var(--card-accent), transparent);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}
.card-back {
  background: linear-gradient(145deg, var(--bg-secondary), var(--bg-tertiary));
  transform: rotateY(180deg);
  box-shadow: var(--shadow-md);
}
.card-back-scroll {
  overflow-y: auto;
  flex: 1;
  padding-right: 4px;
}
.card-back-scroll::-webkit-scrollbar { width: 3px; }
.card-back-scroll::-webkit-scrollbar-thumb { background: var(--glass-border); border-radius: 2px; }

.card-badge {
  position: absolute;
  top: 16px;
  left: 20px;
  font-size: 0.65rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--card-accent);
  background: var(--accent-soft);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
}
.card-word {
  font-size: 3rem;
  font-weight: 900;
  letter-spacing: -0.03em;
  line-height: 1.1;
  background: linear-gradient(135deg, var(--text-primary), var(--card-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 12px;
  animation: wordAppear 0.4s ease-out;
}
@keyframes wordAppear {
  from { opacity: 0; transform: translateY(12px) scale(0.95); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
.card-connotation-front {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 14px;
  border-radius: 20px;
  margin-bottom: 16px;
}
.card-connotation-front[data-connotation="Positive"] { background: var(--correct-bg); color: var(--correct); }
.card-connotation-front[data-connotation="Negative"] { background: var(--wrong-bg); color: var(--wrong); }
.card-connotation-front[data-connotation="Neutral"] { background: var(--surface); color: var(--text-secondary); }
.card-connotation-front[data-connotation="Context-Dependent"] { background: rgba(251,191,36,0.12); color: var(--warning); }
.card-hint {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-style: italic;
}
.card-back-word {
  font-size: 1.6rem;
  font-weight: 800;
  color: var(--card-accent);
  margin-bottom: 20px;
  letter-spacing: -0.02em;
}
.card-section { margin-bottom: 16px; }
.card-section-label {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 4px;
  font-weight: 600;
}
.card-section-value {
  font-size: 0.9rem;
  color: var(--text-primary);
  line-height: 1.5;
}
.card-sentence { font-style: italic; color: var(--text-secondary); }
.card-section-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
}
.card-tag {
  font-size: 0.72rem;
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 500;
}
.card-tag.antonym {
  background: var(--wrong-bg);
  color: var(--wrong);
}

/* ---------- Quiz Area ---------- */
.quiz-area { margin-bottom: 20px; }
.input-row {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
}
#answer-input {
  flex: 1;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  border: 2px solid var(--glass-border);
  background: var(--surface);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  outline: none;
  transition: all var(--transition-fast);
}
#answer-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
#answer-input::placeholder { color: var(--text-muted); }
.btn-primary {
  padding: 14px 24px;
  border: none;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--accent), color-mix(in srgb, var(--accent) 70%, white));
  color: #fff;
  font-weight: 700;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
  white-space: nowrap;
}
.btn-primary:hover { transform: translateY(-1px); box-shadow: var(--shadow-glow); }
.btn-primary:active { transform: translateY(0); }

.btn-secondary {
  padding: 12px 22px;
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  background: var(--surface);
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-secondary:hover { background: var(--surface-hover); color: var(--text-primary); }

/* Result Feedback */
.result-feedback {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  margin-bottom: 14px;
  animation: slideUp 0.3s ease-out;
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}
.result-feedback.correct { background: var(--correct-bg); border: 1px solid rgba(52,211,153,0.3); }
.result-feedback.wrong { background: var(--wrong-bg); border: 1px solid rgba(248,113,113,0.3); }
.result-icon { font-size: 1.3rem; }
.result-text { font-size: 0.88rem; font-weight: 600; }
.result-feedback.correct .result-text { color: var(--correct); }
.result-feedback.wrong .result-text { color: var(--wrong); }

/* Override Buttons */
.override-row {
  display: flex;
  gap: 10px;
  margin-bottom: 14px;
}
.btn-correct {
  flex: 1;
  padding: 12px 16px;
  border: 1px solid rgba(52,211,153,0.3);
  border-radius: var(--radius-md);
  background: var(--correct-bg);
  color: var(--correct);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-correct:hover { background: rgba(52,211,153,0.2); }
.btn-wrong {
  flex: 1;
  padding: 12px 16px;
  border: 1px solid rgba(248,113,113,0.3);
  border-radius: var(--radius-md);
  background: var(--wrong-bg);
  color: var(--wrong);
  font-weight: 700;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.btn-wrong:hover { background: rgba(248,113,113,0.2); }

/* Nav Row */
.nav-row {
  display: flex;
  gap: 10px;
  justify-content: center;
}

/* Keyboard shortcuts */
.shortcuts-hint {
  text-align: center;
  margin-top: 24px;
  font-size: 0.7rem;
  color: var(--text-muted);
}
.shortcuts-hint kbd {
  display: inline-block;
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  background: var(--surface);
  border: 1px solid var(--glass-border);
  border-radius: 4px;
  margin: 0 2px;
}

/* Hidden utility */
.hidden { display: none !important; }

/* ---------- Responsive ---------- */
@media (max-width: 640px) {
  .top-bar-inner { padding: 10px 14px; gap: 8px; flex-wrap: wrap; }
  .logo-text { display: none; }
  .mode-tabs { order: 2; }
  .stats-row { gap: 4px; order: 3; width: 100%; }
  .stat-chip { padding: 4px 8px; font-size: 0.72rem; }
  .stat-label { display: none; }
  .mode-tab { padding: 6px 12px; font-size: 0.75rem; }
  .mode-tab span { display: none; }
  .mode-container { padding: 16px 14px 32px; }
  .card-face { padding: 28px 22px; }
  .card-word { font-size: 2.2rem; }
  .card-section-row { grid-template-columns: 1fr; gap: 12px; }
  .flashcard { min-height: 280px; }
  .input-row { flex-direction: column; }
  .override-row { flex-direction: column; }
  .shortcuts-hint { display: none; }

  /* Study Mode responsive */
  .group-grid { grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 8px; }
  .section-title { font-size: 1.4rem; }
  .study-word { font-size: 2rem; }
  .study-card-header { padding: 20px 18px 16px; }
  .study-card-body { padding: 18px; }
  .study-tags-row { grid-template-columns: 1fr; gap: 12px; }
  .study-actions { flex-direction: column; }
  .drill-container { grid-template-columns: 1fr; gap: 12px; }
  .audio-player-inner { flex-wrap: wrap; }
  .audio-controls { width: 100%; justify-content: center; }
  .audio-info { min-width: 100px; }
  .study-nav-header { flex-direction: column; align-items: flex-start; gap: 8px; }
  .study-card-nav { flex-wrap: wrap; }
}

@media (max-width: 380px) {
  .card-word { font-size: 1.8rem; }
  .flashcard { min-height: 260px; }
  .study-word { font-size: 1.6rem; }
  .group-grid { grid-template-columns: 1fr 1fr; }
}