:root {
  --bg: #fdfbf7;
  --surface: #ffffff;
  --surface-muted: #f6f3ec;
  --border: #e8e2d5;
  --text: #1e242b;
  --text-muted: #646e78;
  --primary: #e63946;
  --primary-hover: #d62839;
  --primary-soft: #ffe8ea;
  --honey: #f59e0b;
  --honey-soft: #fef3c7;
  --success: #16a34a;
  --success-soft: #dcfce7;
  --danger: #dc2626;
  --danger-soft: #fee2e2;
  --info: #2563eb;
  --info-soft: #dbeafe;
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;
  --shadow-sm: 0 2px 8px rgba(30, 36, 43, 0.05);
  --shadow-md: 0 8px 24px rgba(30, 36, 43, 0.08);
  --font: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

/* Header & Navigation */
.app-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(253, 251, 247, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  max-width: 920px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  user-select: none;
}

.brand-icon {
  width: 38px;
  height: 38px;
  border-radius: 11px;
  background: var(--primary-soft);
  display: grid;
  place-items: center;
  font-size: 20px;
}

.brand-title {
  font-weight: 800;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
  position: relative;
  display: inline-block;
}

.squiggly-underline {
  display: block;
  width: 100%;
  height: 5px;
  margin-top: -2px;
}

.brand-badge {
  font-size: 0.72rem;
  font-weight: 700;
  background: var(--honey-soft);
  color: #b45309;
  padding: 3px 8px;
  border-radius: 999px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.nav-tabs {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--surface-muted);
  padding: 4px;
  border-radius: 12px;
  border: 1px solid var(--border);
}

.nav-tab {
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-family: inherit;
  font-weight: 600;
  font-size: 0.9rem;
  padding: 7px 14px;
  border-radius: 9px;
  cursor: pointer;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  gap: 6px;
}

.nav-tab:hover {
  color: var(--text);
}

.nav-tab.active {
  background: var(--surface);
  color: var(--primary);
  box-shadow: var(--shadow-sm);
}

.sync-pill {
  font-size: 0.78rem;
  font-weight: 600;
  padding: 6px 11px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-muted);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.sync-pill:hover {
  border-color: var(--primary);
  color: var(--text);
}

.sync-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #9ca3af;
}

.sync-dot.synced {
  background: var(--success);
}

.sync-dot.syncing {
  background: var(--honey);
  animation: pulse 1s infinite;
}

.sync-dot.local {
  background: var(--info);
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.45; transform: scale(0.85); }
}

/* Main Container */
.main-container {
  max-width: 840px;
  margin: 0 auto;
  padding: 24px 18px 64px;
}

/* Cards */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 20px;
}

.card-title {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

/* Stats Grid */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 20px;
}

.stat-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px 12px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: transform 0.15s ease;
}

.stat-box:hover {
  transform: translateY(-2px);
}

.stat-value {
  font-size: 1.85rem;
  font-weight: 800;
  line-height: 1.1;
}

.stat-label {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-top: 4px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.stat-mastered .stat-value { color: var(--success); }
.stat-learning .stat-value { color: var(--honey); }
.stat-needs-work .stat-value { color: var(--danger); }
.stat-unseen .stat-value { color: var(--info); }

/* Chips & Option Selectors */
.chip-group {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.chip {
  border: 1.5px solid var(--border);
  background: var(--surface-muted);
  color: var(--text);
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 600;
  padding: 10px 16px;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.15s ease;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  user-select: none;
}

.chip:hover {
  border-color: #cbd5e1;
  background: var(--surface);
}

.chip.selected {
  background: var(--primary-soft);
  border-color: var(--primary);
  color: var(--primary);
}

.chip-count {
  font-size: 0.76rem;
  padding: 2px 7px;
  border-radius: 999px;
  background: rgba(0, 0, 0, 0.07);
}

.chip.selected .chip-count {
  background: var(--primary);
  color: #fff;
}

/* Primary & Secondary Buttons */
.btn {
  border: none;
  font-family: inherit;
  font-weight: 700;
  font-size: 1rem;
  padding: 14px 24px;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.15s ease;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 4px 14px rgba(230, 57, 70, 0.3);
}

.btn-primary:hover:not(:disabled) {
  background: var(--primary-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--surface-muted);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--border);
}

.btn-success {
  background: var(--success);
  color: #fff;
  box-shadow: 0 4px 14px rgba(22, 163, 74, 0.25);
}

.btn-block {
  width: 100%;
  font-size: 1.1rem;
  padding: 16px 28px;
}

/* Quiz Stage */
.quiz-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.progress-track {
  width: 100%;
  height: 8px;
  background: var(--surface-muted);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 22px;
  border: 1px solid var(--border);
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--honey));
  border-radius: 999px;
  transition: width 0.3s ease;
}

.speaker-stage {
  text-align: center;
  padding: 28px 20px;
  background: linear-gradient(180deg, #fff9f9 0%, #ffffff 100%);
  border: 2px dashed #f8c6ca;
  border-radius: var(--radius-lg);
  margin-bottom: 20px;
  position: relative;
}

.speaker-stage.correct {
  background: var(--success-soft);
  border: 2px solid #86efac;
}

.speaker-stage.incorrect {
  background: var(--danger-soft);
  border: 2px solid #fca5a5;
}

.speaker-btn-row {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}

.big-speaker-btn {
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: 999px;
  padding: 16px 32px;
  font-family: inherit;
  font-size: 1.15rem;
  font-weight: 800;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 12px;
  box-shadow: 0 8px 22px rgba(230, 57, 70, 0.32);
  transition: transform 0.15s ease, background 0.15s ease;
}

.big-speaker-btn:hover {
  background: var(--primary-hover);
  transform: scale(1.03);
}

.big-speaker-btn:active {
  transform: scale(0.98);
}

.slow-speaker-btn {
  background: var(--surface);
  color: var(--text);
  border: 1.5px solid var(--border);
  border-radius: 999px;
  padding: 13px 20px;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  transition: all 0.15s ease;
}

.slow-speaker-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.audio-source-badge {
  margin-top: 12px;
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 600;
}

/* Hints Bar */
.hints-row {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 16px;
}

.hint-btn {
  border: 1.5px solid var(--border);
  background: var(--surface);
  color: var(--text);
  padding: 9px 16px;
  border-radius: 999px;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 7px;
  transition: all 0.15s ease;
}

.hint-btn:hover, .hint-btn.active {
  background: var(--info-soft);
  border-color: var(--info);
  color: var(--info);
}

.hint-card {
  background: #f0f7ff;
  border: 1px solid #bfdbfe;
  color: #1e3a8a;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  margin-bottom: 18px;
  font-size: 0.98rem;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  animation: fadeIn 0.2s ease;
}

.hint-card-label {
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--info);
  margin-bottom: 2px;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Spelling Input Area */
.spelling-input-wrap {
  position: relative;
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
}

.spelling-input {
  flex: 1;
  font-family: var(--mono);
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  padding: 16px 20px;
  border-radius: var(--radius-md);
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
  outline: none;
  text-align: center;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.spelling-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px var(--primary-soft);
}

.spelling-input::placeholder {
  font-family: var(--font);
  font-size: 1rem;
  letter-spacing: normal;
  font-weight: 500;
  color: #9ca3af;
}

.mic-btn {
  width: 60px;
  border-radius: var(--radius-md);
  border: 2px solid var(--border);
  background: var(--surface);
  font-size: 1.4rem;
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: all 0.15s ease;
}

.mic-btn:hover {
  border-color: var(--primary);
}

.mic-btn.listening {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
  animation: pulse 1s infinite;
}

/* On-screen QWERTY Keyboard */
.onscreen-keyboard {
  background: var(--surface-muted);
  padding: 12px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  margin-bottom: 18px;
  user-select: none;
}

.kb-row {
  display: flex;
  justify-content: center;
  gap: 6px;
  margin-bottom: 6px;
}

.kb-row:last-child {
  margin-bottom: 0;
}

.kb-key {
  min-width: 34px;
  height: 44px;
  padding: 0 8px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  font-family: var(--mono);
  font-weight: 700;
  font-size: 1rem;
  color: var(--text);
  cursor: pointer;
  box-shadow: 0 2px 0 rgba(0,0,0,0.08);
  transition: transform 0.08s ease, background 0.1s ease;
}

.kb-key:active {
  transform: translateY(2px);
  box-shadow: none;
}

.kb-key.kb-wide {
  min-width: 68px;
  font-family: var(--font);
  font-size: 0.85rem;
}

/* Diff & Feedback Display */
.feedback-word {
  font-family: var(--mono);
  font-size: 2.2rem;
  font-weight: 800;
  letter-spacing: 0.05em;
  margin-bottom: 6px;
}

.feedback-phonetic {
  font-size: 0.95rem;
  color: var(--text-muted);
  font-weight: 600;
  margin-bottom: 14px;
}

.diff-container {
  display: inline-flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 4px;
  padding: 10px 14px;
  background: rgba(255, 255, 255, 0.85);
  border-radius: 12px;
  margin: 10px 0;
  font-family: var(--mono);
  font-size: 1.35rem;
  font-weight: 700;
}

.diff-char {
  padding: 2px 6px;
  border-radius: 6px;
}

.diff-match {
  color: var(--success);
  background: #dcfce7;
}

.diff-wrong {
  color: var(--danger);
  background: #fee2e2;
  text-decoration: line-through;
}

.diff-missing {
  color: #b45309;
  background: #fef3c7;
  border-bottom: 2px dashed #f59e0b;
}

.practice-retry-box {
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px solid rgba(0, 0, 0, 0.08);
}

/* Study Explorer List */
.study-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 16px;
}

.search-input {
  flex: 1;
  min-width: 200px;
  padding: 11px 16px;
  border-radius: 12px;
  border: 1.5px solid var(--border);
  font-family: inherit;
  font-size: 0.95rem;
}

.word-list-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
}

.study-word-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px 20px;
  transition: box-shadow 0.15s ease;
}

.study-word-card:hover {
  box-shadow: var(--shadow-md);
}

.study-word-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 8px;
}

.study-word-title {
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.study-phonetic {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--primary);
  background: var(--primary-soft);
  padding: 2px 9px;
  border-radius: 999px;
}

.study-meta {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 8px;
  font-weight: 600;
}

.study-def {
  font-size: 0.95rem;
  margin-bottom: 6px;
}

.study-sentence {
  font-size: 0.88rem;
  color: var(--text-muted);
  font-style: italic;
}

.star-btn {
  background: transparent;
  border: none;
  font-size: 1.3rem;
  cursor: pointer;
  line-height: 1;
  padding: 4px;
}

/* Voice Bee Cadence Bar */
.bee-cadence-bar {
  background: var(--surface-muted);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-md);
  padding: 10px 14px;
  margin-bottom: 14px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  animation: fadeIn 0.2s ease;
}

.bee-cadence-bar.listening {
  background: #fff8f8;
  border-color: #fca5a5;
}

.cadence-steps {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
}

.cadence-pill {
  font-size: 0.78rem;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-muted);
  display: inline-flex;
  align-items: center;
  gap: 5px;
  transition: all 0.15s ease;
}

.cadence-pill.active {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-soft);
}

.cadence-pill.done {
  border-color: #86efac;
  background: var(--success-soft);
  color: var(--success);
}

.cadence-arrow {
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 700;
}

.cadence-subtext {
  text-align: center;
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 600;
}

/* Responsive adjustments */
@media (max-width: 640px) {
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .header-inner {
    justify-content: center;
  }
  .spelling-input {
    font-size: 1.25rem;
  }
  .feedback-word {
    font-size: 1.75rem;
  }
  .kb-key {
    min-width: 28px;
    height: 40px;
    padding: 0 5px;
    font-size: 0.9rem;
  }
}