:root {
  --bg: #0f1117;
  --bg-card: #1a1d27;
  --bg-card-hover: #22263a;
  --bg-input: #252836;
  --text: #e8e8ee;
  --text-dim: #8b8fa3;
  --text-muted: #555a6e;
  --border: #2a2e3f;
  --accent: #6c5ce7;
  --accent-dim: rgba(108, 92, 231, 0.15);
  --green: #00b894;
  --green-dim: rgba(0, 184, 148, 0.15);
  --red: #e74c3c;
  --red-dim: rgba(231, 76, 60, 0.15);
  --orange: #e8913a;
  --orange-dim: rgba(232, 145, 58, 0.15);
  --blue: #4a90d9;
  --blue-dim: rgba(74, 144, 217, 0.15);
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 2px 16px rgba(0,0,0,0.3);
  --font: 'Segoe UI', system-ui, -apple-system, sans-serif;
  --font-jp: 'Hiragino Kaku Gothic Pro', 'Yu Gothic', 'Meiryo', sans-serif;
  --transition: 0.2s ease;
}

[data-theme="light"] {
  --bg: #f5f6fa;
  --bg-card: #ffffff;
  --bg-card-hover: #f0f1f6;
  --bg-input: #eef0f5;
  --text: #1a1d27;
  --text-dim: #555a6e;
  --text-muted: #8b8fa3;
  --border: #dfe1e8;
  --shadow: 0 2px 16px rgba(0,0,0,0.08);
}

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

html { font-size: 16px; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  min-height: 100dvh;
  transition: background var(--transition), color var(--transition);
}

#app {
  max-width: 600px;
  margin: 0 auto;
  padding: 0 16px 32px;
}

/* Header */
#header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 0;
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 100;
  border-bottom: 1px solid var(--border);
  margin-bottom: 16px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 8px;
  min-width: 0;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

#header-title {
  font-size: 1.15rem;
  font-weight: 700;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.icon-btn {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
}

.icon-btn:hover { background: var(--bg-card-hover); }

.streak-badge {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.9rem;
  font-weight: 600;
  padding: 4px 10px;
  background: var(--orange-dim);
  border-radius: 20px;
  color: var(--orange);
}

/* Screens */
.screen { display: none; }
.screen.active { display: block; }

/* Stats bar */
.stats-bar {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
}

.stat {
  flex: 1;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px;
  text-align: center;
}

.stat-num {
  display: block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
}

.stat-label {
  display: block;
  font-size: 0.7rem;
  color: var(--text-dim);
  margin-top: 2px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* Section title */
.section-title {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-dim);
  margin: 20px 0 12px;
}

/* Mode tabs (Verbs / Adjectives) */
.mode-tabs {
  display: flex;
  gap: 4px;
  margin-bottom: 16px;
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 4px;
  border: 1px solid var(--border);
}

.mode-tab {
  flex: 1;
  padding: 10px;
  border: none;
  border-radius: 6px;
  background: transparent;
  color: var(--text-dim);
  font-size: 0.9rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
}

.mode-tab.active {
  background: var(--accent);
  color: #fff;
}

.mode-tab:hover:not(.active) {
  background: var(--bg-card-hover);
}

/* Chapter grid */
.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 10px;
}

.chapter-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  cursor: pointer;
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.chapter-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.chapter-card-title {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.chapter-card-sub {
  font-size: 0.75rem;
  color: var(--text-dim);
  margin-bottom: 8px;
}

.chapter-card-forms {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin-bottom: 10px;
}

.form-pill {
  font-family: var(--font-jp);
  font-size: 0.65rem;
  padding: 3px 8px;
  border-radius: 10px;
  font-weight: 700;
  letter-spacing: 0;
  white-space: nowrap;
}

.chapter-progress {
  height: 4px;
  background: var(--bg-input);
  border-radius: 2px;
  overflow: hidden;
}

.chapter-progress-fill {
  height: 100%;
  background: var(--green);
  border-radius: 2px;
  transition: width 0.4s ease;
}

.chapter-card-due {
  font-size: 0.7rem;
  color: var(--accent);
  margin-top: 6px;
  font-weight: 600;
}

/* Study screen */
.study-toolbar {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
}

.study-progress {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: 1;
}

.study-progress-bar {
  flex: 1;
  height: 6px;
  background: var(--bg-input);
  border-radius: 3px;
  overflow: hidden;
}

.study-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 3px;
  transition: width 0.3s ease;
}

.study-progress-text {
  font-size: 0.8rem;
  color: var(--text-dim);
  white-space: nowrap;
}

.btn-undo {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-card);
  color: var(--text-dim);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
  flex-shrink: 0;
}

.btn-undo:hover {
  background: var(--bg-card-hover);
  color: var(--text);
  border-color: var(--accent);
}

.save-indicator {
  text-align: center;
  font-size: 0.7rem;
  color: var(--green);
  padding: 4px 0;
  font-weight: 600;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.save-indicator.show {
  opacity: 1;
}

/* Card */
.card-container {
  perspective: 1000px;
}

.card {
  background: color-mix(in srgb, var(--form-color, var(--accent)) 8%, var(--bg-card));
  border: 1px solid var(--border);
  border-left: 5px solid var(--form-color, var(--accent));
  border-right: 5px solid transparent;
  border-radius: var(--radius);
  padding: 28px 24px;
  box-shadow: var(--shadow);
  min-height: 340px;
  display: flex;
  flex-direction: column;
  transition: background 0.3s ease, border-color 0.3s ease;
}

.card.negative-form {
  border-right-color: #e74c3c;
}

.card-front, .card-back {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  flex: 1;
}

.form-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 24px;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.3px;
  border: 2px solid currentColor;
  white-space: nowrap;
}

.form-badge .form-symbol {
  font-family: var(--font-jp);
  font-size: 0.95rem;
  font-weight: 800;
  line-height: 1;
}

.card-kanji {
  font-family: var(--font-jp);
  font-size: 2.8rem;
  font-weight: 700;
  line-height: 1.2;
  text-align: center;
}

.card-reading {
  font-family: var(--font-jp);
  font-size: 1.1rem;
  color: var(--text-dim);
}

.card-meaning {
  font-size: 0.95rem;
  color: var(--text-dim);
  text-align: center;
}

.card-conjugated {
  font-family: var(--font-jp);
  font-size: 1.8rem;
  font-weight: 700;
  text-align: center;
  line-height: 1.3;
}

.card-prompt {
  font-size: 1rem;
  font-weight: 600;
  color: var(--form-color, var(--accent));
  text-align: center;
  margin-top: 4px;
}

.card-context {
  font-size: 1.15rem;
  color: var(--text-muted);
  font-style: italic;
  text-align: center;
  margin-top: -4px;
}

.card-context.context-prominent {
  font-size: 1.5rem;
  color: var(--text);
  font-style: normal;
  font-weight: 600;
  margin-top: 16px;
  margin-bottom: 8px;
  line-height: 1.4;
}

/* Reveal area (default mode) */
.hint-area {
  margin-top: 12px;
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  background: var(--bg-card-hover, rgba(128,128,128,0.08));
  border-left: 3px solid var(--form-color, var(--accent));
  font-size: 0.88rem;
  line-height: 1.6;
  color: var(--text);
  text-align: left;
}

.hint-area .hint-label {
  font-weight: 700;
  color: var(--text-dim);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 4px;
}

.hint-area .hint-step {
  margin: 2px 0;
}

.reveal-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  margin-top: 16px;
}

.reveal-buttons {
  display: flex;
  gap: 10px;
  align-items: center;
}

.btn-hint {
  padding: 14px 24px;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 700;
  cursor: pointer;
  border: 2px solid var(--border);
  background: transparent;
  color: var(--text-dim);
  transition: all var(--transition);
}

.btn-hint:hover { border-color: var(--accent); color: var(--accent); transform: translateY(-1px); }
.btn-hint:disabled { opacity: 0.4; cursor: default; transform: none; }

.btn-reveal {
  padding: 14px 40px;
  border-radius: var(--radius-sm);
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  border: none;
  background: var(--accent);
  color: #fff;
  transition: all var(--transition);
}

.btn-reveal:hover { filter: brightness(1.1); transform: translateY(-1px); }

.reveal-hint {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Answer */
.answer-area {
  display: flex;
  gap: 8px;
  width: 100%;
  max-width: 360px;
  margin-top: 8px;
}

.answer-input {
  flex: 1;
  padding: 10px 14px;
  font-size: 1.15rem;
  font-family: var(--font-jp);
  background: var(--bg-input);
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  outline: none;
  transition: border-color var(--transition);
}

.answer-input:focus {
  border-color: var(--accent);
}

.answer-input.correct {
  border-color: var(--green);
  background: var(--green-dim);
}

.answer-input.incorrect {
  border-color: var(--red);
  background: var(--red-dim);
}

/* Buttons */
.btn-primary, .btn-secondary {
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all var(--transition);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
}

.btn-primary:hover { filter: brightness(1.1); }

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

.btn-secondary:hover { background: var(--bg-card-hover); color: var(--text); }

.btn-danger {
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  border: 1px solid var(--red);
  background: var(--red-dim);
  color: var(--red);
  transition: all var(--transition);
}

.btn-danger:hover { background: var(--red); color: #fff; }

/* Result area */
.result-area {
  width: 100%;
  max-width: 360px;
  text-align: center;
}

.result-icon {
  font-size: 2.5rem;
  margin-bottom: 8px;
}

.result-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid var(--border);
  font-size: 1rem;
}

.result-label {
  color: var(--text-dim);
}

.user-answer {
  font-family: var(--font-jp);
  font-weight: 600;
}

.correct-answer {
  font-family: var(--font-jp);
  font-weight: 600;
  color: var(--green);
}

/* Explanation */
.card-explanation {
  width: 100%;
  max-width: 360px;
  margin-top: 12px;
  padding: 12px 16px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  line-height: 1.6;
  color: var(--text-dim);
  animation: slideUp 0.3s ease;
}

.card-explanation .ex-rule {
  margin-bottom: 6px;
  color: var(--text);
}

.card-explanation .ex-steps {
  font-family: var(--font-jp);
  font-size: 0.95rem;
  color: var(--text);
  letter-spacing: 0.3px;
}

.card-explanation .ex-hl {
  color: var(--accent);
  font-weight: 700;
}

/* Example sentence */
.card-example-sentence {
  width: 100%;
  max-width: 360px;
  margin-top: 14px;
  padding: 12px 16px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  animation: slideUp 0.3s ease;
}

.card-example-sentence .example-label {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.card-example-sentence .example-jp {
  font-family: var(--font-jp);
  font-size: 1.15rem;
  color: var(--text);
  margin-bottom: 4px;
  line-height: 1.5;
}

.card-example-sentence .example-en {
  font-size: 0.9rem;
  color: var(--text-dim);
  font-style: italic;
  line-height: 1.4;
}

/* Grade buttons */
.grade-buttons {
  display: flex;
  gap: 8px;
  margin-top: 16px;
  flex-wrap: wrap;
  justify-content: center;
}

.btn-grade {
  flex: 1;
  min-width: 60px;
  padding: 10px 8px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
}

.grade-key {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 20px;
  height: 20px;
  border-radius: 4px;
  background: rgba(255,255,255,0.25);
  font-size: 0.7rem;
  font-weight: 800;
  line-height: 1;
  flex-shrink: 0;
}

.btn-again { background: #e74c3c; }
.btn-good  { background: #27ae60; }
.btn-easy  { background: #3498db; }

.btn-grade:hover { filter: brightness(1.15); transform: translateY(-1px); }

/* Session complete */
.session-complete {
  text-align: center;
  padding: 40px 20px;
}

.complete-icon {
  font-size: 4rem;
  margin-bottom: 12px;
}

.session-complete h2 {
  font-size: 1.5rem;
  margin-bottom: 20px;
}

.session-stats {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-bottom: 28px;
}

.session-stats .stat {
  min-width: 80px;
}

/* Reference screen */
.ref-tabs {
  display: flex;
  gap: 4px;
  margin-bottom: 16px;
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  padding: 4px;
  border: 1px solid var(--border);
}

.ref-tab {
  flex: 1;
  padding: 8px;
  border: none;
  border-radius: 6px;
  background: transparent;
  color: var(--text-dim);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
}

.ref-tab.active {
  background: var(--accent);
  color: #fff;
}

.ref-content {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.ref-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.ref-table th {
  background: var(--bg-input);
  padding: 10px 12px;
  text-align: left;
  font-weight: 600;
  color: var(--text-dim);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  position: sticky;
  top: 0;
}

.ref-table td {
  padding: 8px 12px;
  border-top: 1px solid var(--border);
  font-family: var(--font-jp);
}

.ref-table tr:hover td {
  background: var(--bg-card-hover);
}

/* Build Your Own */
.custom-section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.custom-verbs-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  padding: 0;
  overflow: hidden;
}

.custom-chapter-group {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
}

.custom-chapter-group:last-child {
  border-bottom: none;
}

.custom-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 20px;
  margin-bottom: 8px;
}

.custom-header .section-title {
  margin: 0;
}

.custom-header:first-child {
  margin-top: 0;
}

.custom-chapter-header {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 2px;
}

.custom-check-item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background var(--transition);
  font-size: 0.85rem;
  user-select: none;
}

.custom-check-item:hover {
  background: var(--bg-card-hover);
}

.custom-check-item input[type="checkbox"] {
  width: 16px;
  height: 16px;
  accent-color: var(--accent);
  cursor: pointer;
  flex-shrink: 0;
}

.custom-check-label {
  color: var(--text);
}

.custom-check-kanji {
  font-family: var(--font-jp);
  color: var(--text);
  font-weight: 600;
}

.custom-check-sub {
  color: var(--text-dim);
  font-size: 0.75rem;
}

.btn-toggle-all {
  font-size: 0.7rem;
  padding: 4px 10px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--text-dim);
  cursor: pointer;
  margin-left: 8px;
  font-weight: 600;
  vertical-align: middle;
  transition: all var(--transition);
}

.btn-toggle-all:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.custom-start-section {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-top: 20px;
  padding: 16px 0;
}

.custom-count {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-dim);
}

.btn-start-custom {
  padding: 12px 32px;
  font-size: 1rem;
}

.btn-start-custom:disabled {
  opacity: 0.4;
  cursor: default;
}

/* Reset section */
.reset-section {
  margin-top: 32px;
  text-align: center;
  padding: 20px 0;
  border-top: 1px solid var(--border);
}

/* Settings */
.settings-panel {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.setting-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  cursor: pointer;
  transition: background var(--transition);
}

.setting-row:hover { background: var(--bg-card-hover); }

.setting-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.setting-label {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text);
}

.setting-desc {
  font-size: 0.75rem;
  color: var(--text-dim);
}

.setting-toggle {
  width: 44px;
  height: 24px;
  appearance: none;
  -webkit-appearance: none;
  background: var(--border);
  border-radius: 12px;
  position: relative;
  cursor: pointer;
  transition: background 0.2s ease;
  flex-shrink: 0;
}

.setting-toggle::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: #fff;
  transition: transform 0.2s ease;
}

.setting-toggle:checked {
  background: var(--accent);
}

.setting-toggle:checked::after {
  transform: translateX(20px);
}

/* Vimium compatibility: hidden input to capture focus */
.key-capture {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
  padding: 0;
  border: 0;
  pointer-events: none;
  overflow: hidden;
}

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

/* Responsive */
@media (max-width: 480px) {
  #app { padding: 0 12px 24px; }

  .chapter-grid {
    grid-template-columns: 1fr 1fr;
  }

  .card { padding: 20px 16px; min-height: 300px; }
  .card-kanji { font-size: 2.2rem; }

  .stats-bar { flex-wrap: wrap; }
  .stat { min-width: calc(50% - 4px); }

  .grade-buttons { gap: 6px; }
  .btn-grade { padding: 10px 4px; font-size: 0.8rem; }
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.screen.active {
  animation: fadeIn 0.25s ease;
}

@keyframes pop {
  0% { transform: scale(0.8); opacity: 0; }
  50% { transform: scale(1.05); }
  100% { transform: scale(1); opacity: 1; }
}

.result-icon {
  animation: pop 0.3s ease;
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.card-back {
  animation: slideUp 0.25s ease;
}