/* ── Reset & Variables ── */
:root {
  --bg: #f8f9fa;
  --surface: #ffffff;
  --text: #1a1a2e;
  --text-secondary: #6c757d;
  --primary: #4361ee;
  --primary-hover: #3a56d4;
  --success: #06d6a0;
  --warning: #ffd166;
  --danger: #ef476f;
  --border: #dee2e6;
  --radius: 12px;
  --shadow: 0 2px 8px rgba(0,0,0,0.08);

  /* Category colors */
  --cat-protocol: #4361ee;
  --cat-concept: #7209b7;
  --cat-tool: #06d6a0;
  --cat-project: #ffd166;
  --cat-finding: #ef476f;
}

@media (prefers-color-scheme: dark) {
  :root.auto-dark {
    --bg: #1a1a2e;
    --surface: #16213e;
    --text: #e8e8e8;
    --text-secondary: #adb5bd;
    --border: #2d3748;
    --shadow: 0 2px 8px rgba(0,0,0,0.3);
  }
}

.dark {
  --bg: #1a1a2e;
  --surface: #16213e;
  --text: #e8e8e8;
  --text-secondary: #adb5bd;
  --border: #2d3748;
  --shadow: 0 2px 8px rgba(0,0,0,0.3);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

/* ── Screens ── */
.screen { max-width: 640px; margin: 0 auto; padding: 24px 16px; }
.hidden { display: none !important; }

/* ── Onboarding ── */
#onboarding {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  text-align: center;
}

#onboarding h1 { font-size: 2rem; margin-bottom: 8px; }
.subtitle { color: var(--text-secondary); margin-bottom: 48px; font-size: 1.1rem; }

.level-picker { width: 100%; max-width: 400px; }
.level-picker h2 { font-size: 1.1rem; margin-bottom: 16px; color: var(--text-secondary); }

.level-btn {
  display: block;
  width: 100%;
  padding: 16px 20px;
  margin-bottom: 12px;
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius);
  cursor: pointer;
  text-align: left;
  transition: border-color 0.2s, transform 0.1s;
}

.level-btn:hover { border-color: var(--primary); transform: translateY(-1px); }
.level-btn strong { display: block; font-size: 1.05rem; margin-bottom: 4px; color: var(--text); }
.level-btn span { font-size: 0.9rem; color: var(--text-secondary); }

/* ── Header ── */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

header h1 { font-size: 1.3rem; }

.header-actions button {
  background: none;
  border: none;
  font-size: 1.4rem;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 4px 8px;
}

/* ── Deck Selector ── */
.deck-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}

.mode-toggle {
  display: flex;
  gap: 4px;
  margin-bottom: 12px;
}

.mode-toggle button {
  padding: 6px 14px;
  border: 1px solid var(--border);
  background: var(--surface);
  cursor: pointer;
  font-size: 0.85rem;
  border-radius: 6px;
  color: var(--text);
}

.mode-toggle button.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.category-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 16px;
}

.cat-chip {
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  border: 2px solid transparent;
  cursor: pointer;
  font-weight: 500;
  transition: opacity 0.2s;
}

.cat-chip.active { opacity: 1; }
.cat-chip:not(.active) { opacity: 0.4; }

.cat-chip[data-cat="protocol"] { background: var(--cat-protocol); color: white; }
.cat-chip[data-cat="concept"] { background: var(--cat-concept); color: white; }
.cat-chip[data-cat="tool"] { background: var(--cat-tool); color: #1a1a2e; }
.cat-chip[data-cat="project"] { background: var(--cat-project); color: #1a1a2e; }
.cat-chip[data-cat="finding"] { background: var(--cat-finding); color: white; }

/* Source filter chips */
.source-filters {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.filter-label {
  font-size: 0.8rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.source-chip {
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  cursor: pointer;
  font-weight: 500;
  transition: opacity 0.2s;
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
}

.source-chip.active { opacity: 1; border-color: var(--primary); }
.source-chip:not(.active) { opacity: 0.4; }

/* ── Progress Bar ── */
.progress-bar-container {
  margin-bottom: 16px;
}

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

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

.progress-text {
  display: flex;
  justify-content: space-between;
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* ── Card ── */
.card-container {
  perspective: 1000px;
  margin-bottom: 20px;
}

.card {
  position: relative;
  width: 100%;
  min-height: 240px;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.5s;
}

.card.flipped { transform: rotateY(180deg); }

.card-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  display: flex;
  flex-direction: column;
}

.card-back {
  transform: rotateY(180deg);
}

.card-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.card-category {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.card-source {
  font-size: 0.65rem;
  font-weight: 500;
  padding: 2px 8px;
  border-radius: 10px;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

.card-source.source-api {
  background: #e3f2fd;
  color: #1565c0;
}

.card-source.source-in-session {
  background: #e8f5e9;
  color: #2e7d32;
}

.card-question, .card-answer {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-size: 1.1rem;
  line-height: 1.5;
}

.card-answer { font-size: 1rem; }

.card-hint {
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-style: italic;
  margin-top: 12px;
}

.hint-btn {
  background: none;
  border: 1px dashed var(--border);
  padding: 6px 16px;
  border-radius: 6px;
  cursor: pointer;
  color: var(--text-secondary);
  font-size: 0.85rem;
  margin-top: 12px;
  align-self: center;
}

.tap-hint {
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-align: center;
  margin-top: 8px;
}

/* ── Assessment Buttons ── */
.assessment {
  display: flex;
  gap: 8px;
  justify-content: center;
  margin-top: 12px;
}

.assess-btn {
  flex: 1;
  padding: 12px 8px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  color: white;
  transition: transform 0.1s;
}

.assess-btn:active { transform: scale(0.95); }
.assess-btn.again { background: var(--danger); }
.assess-btn.hard { background: var(--warning); color: #1a1a2e; }
.assess-btn.good { background: var(--success); color: #1a1a2e; }
.assess-btn.easy { background: var(--primary); }

/* ── Related Cards ── */
.related-cards {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
}

.related-cards h4 {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.related-link {
  display: inline-block;
  font-size: 0.8rem;
  color: var(--primary);
  cursor: pointer;
  margin-right: 8px;
  text-decoration: underline;
}

/* ── Empty / Done State ── */
.empty-state {
  text-align: center;
  padding: 48px 24px;
  color: var(--text-secondary);
}

.empty-state h2 { margin-bottom: 8px; color: var(--text); }

/* ── Session Stats ── */
.stats-bar {
  display: flex;
  justify-content: space-around;
  padding: 12px;
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin-top: 16px;
}

.stat { text-align: center; }
.stat-value { font-size: 1.3rem; font-weight: 700; color: var(--primary); }
.stat-label { font-size: 0.75rem; color: var(--text-secondary); }

/* ── Settings Panel ── */
#settings-panel {
  min-height: 100vh;
}

.settings-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}

.settings-header h2 { font-size: 1.3rem; }

.back-btn {
  background: none;
  border: none;
  font-size: 1.1rem;
  cursor: pointer;
  color: var(--text-secondary);
  padding: 4px 8px;
}

.setting-group {
  margin-bottom: 24px;
}

.setting-group h3 {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 8px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.setting-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 16px;
  background: var(--surface);
  border-radius: 8px;
  margin-bottom: 8px;
}

.setting-row label { font-size: 0.95rem; }

.toggle {
  position: relative;
  width: 48px;
  height: 26px;
}

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

.toggle-slider {
  position: absolute;
  inset: 0;
  background: var(--border);
  border-radius: 13px;
  cursor: pointer;
  transition: background 0.2s;
}

.toggle-slider::before {
  content: '';
  position: absolute;
  height: 20px;
  width: 20px;
  left: 3px;
  bottom: 3px;
  background: white;
  border-radius: 50%;
  transition: transform 0.2s;
}

.toggle input:checked + .toggle-slider { background: var(--primary); }
.toggle input:checked + .toggle-slider::before { transform: translateX(22px); }

.settings-btn-row {
  display: flex;
  gap: 8px;
}

.settings-action {
  flex: 1;
  padding: 10px;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--text);
}

.settings-action.danger { color: var(--danger); border-color: var(--danger); }

/* ── Responsive ── */
@media (max-width: 480px) {
  .screen { padding: 16px 12px; }
  header h1 { font-size: 1.1rem; }
  .card-face { padding: 16px; }
  .assessment { flex-wrap: wrap; }
  .assess-btn { min-width: calc(50% - 4px); }
}