:root {
  --bg: #f0f4f8;
  --surface: #fff;
  --border: #dde3ec;
  --primary: #1a73e8;
  --primary-hover: #1557b0;
  --primary-light: #e8f0fe;
  --text: #1c2333;
  --text-muted: #6b7280;
  --correct: #1e8e3e;
  --incorrect: #d93025;
  --mastery-not: #e2e8f0;
  --mastery-attempted: #f9ab00;
  --mastery-familiar: #1a73e8;
  --mastery-proficient: #137333;
  --mastery-mastered: #0d652d;
  --radius: 10px;
  --shadow: 0 1px 4px rgba(0,0,0,0.07);
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

/* ── Header ── */
.header {
  background: #1c2b4a;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 52px;
  position: sticky;
  top: 0;
  z-index: 10;
}
.logo {
  font-weight: 800;
  font-size: 1.1rem;
  color: #fff;
  text-decoration: none;
  letter-spacing: -0.01em;
}
.nav { display: flex; gap: 0.25rem; }
.nav a {
  color: rgba(255,255,255,0.7);
  text-decoration: none;
  padding: 0.4rem 0.9rem;
  border-radius: 6px;
  font-size: 0.9rem;
  transition: background 0.15s, color 0.15s;
}
.nav a:hover { color: #fff; background: rgba(255,255,255,0.1); }
.nav a.active { color: #fff; background: rgba(255,255,255,0.18); font-weight: 600; }

/* ── Layout ── */
.main { max-width: 1200px; margin: 0 auto; padding: 2rem 1.5rem; min-height: 80vh; }

.screen { display: block; }
.screen.hidden { display: none; }
.hidden { display: none !important; }

h1 { font-size: 1.5rem; margin: 0 0 0.25rem; font-weight: 700; }
h2 { font-size: 1.25rem; margin: 0 0 0.75rem; font-weight: 700; }
.subtitle { color: var(--text-muted); margin: 0 0 1.5rem; font-size: 0.95rem; }

/* ── Progress summary card ── */
.mastery-summary {
  background: linear-gradient(135deg, #1c2b4a 0%, #1a73e8 100%);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.75rem;
  color: #fff;
  box-shadow: 0 4px 16px rgba(26,115,232,0.25);
}
.mastery-summary-label {
  font-size: 0.8rem;
  opacity: 0.75;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin-bottom: 0.4rem;
}
.mastery-summary-count {
  font-size: 1.6rem;
  font-weight: 800;
  margin-bottom: 0.75rem;
  line-height: 1;
}
.mastery-summary-count span {
  font-size: 0.85rem;
  font-weight: 400;
  opacity: 0.75;
}
.progress-track {
  height: 10px;
  background: rgba(255,255,255,0.25);
  border-radius: 99px;
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, #a8edbc, #34d399);
  border-radius: 99px;
  transition: width 0.6s ease;
  min-width: 3px;
}

/* ── Category groups ── */
.type-group { margin-bottom: 1.75rem; }
.type-group-header {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.65rem;
}
.type-group-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--primary);
  flex-shrink: 0;
}
.type-group-name {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--text);
}
.type-group-line {
  flex: 1;
  height: 1px;
  background: var(--border);
}
/* Cycle through category accent colors */
.type-group:nth-child(1)  .type-group-dot { background: #1a73e8; }
.type-group:nth-child(2)  .type-group-dot { background: #e91e8c; }
.type-group:nth-child(3)  .type-group-dot { background: #f9ab00; }
.type-group:nth-child(4)  .type-group-dot { background: #1e8e3e; }
.type-group:nth-child(5)  .type-group-dot { background: #e53935; }
.type-group:nth-child(6)  .type-group-dot { background: #8e24aa; }
.type-group:nth-child(7)  .type-group-dot { background: #00897b; }
.type-group:nth-child(8)  .type-group-dot { background: #f4511e; }
.type-group:nth-child(9)  .type-group-dot { background: #1565c0; }
.type-group:nth-child(10) .type-group-dot { background: #558b2f; }
.type-group:nth-child(11) .type-group-dot { background: #6d4c41; }
.type-group:nth-child(12) .type-group-dot { background: #00838f; }
.type-group:nth-child(13) .type-group-dot { background: #ad1457; }
.type-group:nth-child(14) .type-group-dot { background: #4527a0; }
.type-group:nth-child(15) .type-group-dot { background: #2e7d32; }
.type-group:nth-child(16) .type-group-dot { background: #d84315; }
.type-group:nth-child(17) .type-group-dot { background: #0277bd; }
.type-group:nth-child(18) .type-group-dot { background: #c62828; }
.type-group:nth-child(19) .type-group-dot { background: #4a148c; }
.type-group:nth-child(20) .type-group-dot { background: #1b5e20; }

/* ── Type grid ── */
.type-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(145px, 1fr));
  gap: 0.55rem;
}
.type-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid #c8cdd6;
  border-radius: var(--radius);
  padding: 0.6rem 0.75rem;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  transition: box-shadow 0.15s, transform 0.1s;
}
.type-card:hover { box-shadow: 0 4px 16px rgba(0,0,0,0.12); transform: translateY(-2px); border-left-width: 5px; }
.type-card .name { font-weight: 600; font-size: 0.82rem; line-height: 1.3; }
.type-card .name span { font-weight: 400; color: var(--text-muted); font-size: 0.75rem; }
.type-card .level {
  display: inline-block;
  padding: 0.15em 0.45em;
  border-radius: 4px;
  font-size: 0.65rem;
  font-weight: 600;
  text-transform: capitalize;
  width: fit-content;
}

/* Card action buttons */
.card-actions {
  display: flex;
  gap: 0.35rem;
  margin-top: 0.5rem;
  flex-wrap: wrap;
}
.card-btn-practice, .card-btn-learn {
  font-size: 0.68rem;
  font-weight: 600;
  padding: 0.2em 0.55em;
  border-radius: 4px;
  text-decoration: none;
  transition: background 0.12s;
}
.card-btn-practice {
  background: var(--bg);
  color: var(--primary);
  border: 1px solid var(--primary);
}
.card-btn-practice:hover { background: var(--primary-light); }
.card-btn-learn {
  background: var(--amber-light, #fef7e0);
  color: #92600a;
  border: 1px solid #f9ab00;
}
.card-btn-learn:hover { background: #fde68a; }

/* Picker chip wrapper + learn icon */
.picker-chip-wrap { display: inline-flex; flex-direction: column; align-items: center; gap: 0.15rem; }
.picker-learn-link {
  font-size: 0.72rem;
  text-decoration: none;
  opacity: 0.65;
  transition: opacity 0.12s;
  line-height: 1;
  color: var(--primary);
  font-weight: 600;
}
.picker-learn-link:hover { opacity: 1; }

/* Card left-border colors per level */
.type-card.level-not_started   { border-left-color: #c8cdd6; }
.type-card.level-attempted     { border-left-color: #f9ab00; }
.type-card.level-familiar      { border-left-color: #1a73e8; }
.type-card.level-proficient    { border-left-color: #1e8e3e; }
.type-card.level-mastered      { border-left-color: #0d652d; background: #f0faf4; }

.level-not_started  { background: #f0f2f5; color: #6b7280; }
.level-attempted    { background: #fef7e0; color: #92600a; }
.level-familiar     { background: #e8f0fe; color: #1557b0; }
.level-proficient   { background: #e6f4ea; color: #137333; }
.level-mastered     { background: #ceead6; color: #0d652d; }

/* ── Practice setup ── */
.practice-options { margin: 0.75rem 0 1rem; display: flex; flex-wrap: wrap; align-items: center; gap: 0.75rem; }
.practice-options label { font-size: 0.9rem; font-weight: 500; }
.practice-options select {
  padding: 0.4em 0.6em;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--surface);
  font-size: 0.9rem;
}

/* ── Type picker (grouped) ── */
.type-picker {
  margin: 0.5rem 0 1rem;
  max-height: 40vh;
  overflow-y: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.5rem 0.75rem;
  background: var(--surface);
}
.picker-unit-section { margin-bottom: 1rem; }
.picker-unit-header {
  font-size: 0.72rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.07em; color: var(--text-muted);
  padding: 0.3rem 0 0.5rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 0.5rem;
}
.picker-subtype-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 0.5rem;
}
.picker-subtype-card {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.55rem 0.8rem;
  border: 2px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  cursor: pointer;
  transition: border-color 0.12s, background 0.12s;
  font-family: inherit;
  text-align: left;
  gap: 0.5rem;
}
.picker-subtype-card:hover { border-color: var(--primary); background: var(--primary-light); }
.picker-subtype-card.active {
  border-color: var(--primary); background: var(--primary); color: #fff;
}
.picker-subtype-card.active .picker-subtype-id { color: rgba(255,255,255,0.75); }
.picker-subtype-name { font-size: 0.85rem; font-weight: 600; flex: 1; }
.picker-subtype-id { font-size: 0.72rem; color: var(--text-muted); white-space: nowrap; }
.picker-learn-link {
  font-size: 0.8rem; opacity: 0.55; text-decoration: none;
  flex-shrink: 0;
}
.picker-learn-link:hover { opacity: 1; }
/* legacy chip support */
.picker-chip-wrap { display: inline-flex; flex-direction: column; align-items: center; gap: 0.15rem; }

/* ── Buttons ── */
.btn {
  padding: 0.5rem 1.1rem;
  border-radius: 7px;
  border: 1px solid var(--border);
  background: var(--surface);
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  display: inline-block;
  transition: background 0.12s, box-shadow 0.12s;
}
.btn:hover { background: #f1f5fb; }
.btn-primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
  box-shadow: 0 2px 6px rgba(26,115,232,0.25);
}
.btn-primary:hover { background: var(--primary-hover); box-shadow: 0 3px 10px rgba(26,115,232,0.35); }

/* ── Progress bar (practice session) ── */
.progress-bar {
  margin-bottom: 1rem;
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.02em;
}

/* ── Question card ── */
.question-card, .feedback-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1rem;
  box-shadow: var(--shadow);
}
.question-card { border-top: 3px solid var(--primary); }
.question-text { font-size: 1.05rem; line-height: 1.6; margin: 0 0 1.25rem; font-weight: 500; }

/* ── Diagram / table ── */
.diagram-container { margin: 0 0 1.1rem; }
.diagram-table {
  border-collapse: collapse;
  font-size: 0.92rem;
  width: auto;
  max-width: 100%;
  margin-bottom: 0;
}
.diagram-table th, .diagram-table td {
  border: 1px solid var(--border);
  padding: 0.4rem 0.85rem;
  text-align: left;
  white-space: nowrap;
}
.diagram-table th {
  background: #f1f5fb;
  font-weight: 700;
  font-size: 0.82rem;
  color: var(--text);
}
.diagram-table tr:nth-child(even) td { background: #f7f9fc; }
.diagram-text {
  font-style: italic;
  color: var(--text-muted);
  font-size: 0.9rem;
  padding: 0.5rem 0.75rem;
  border-left: 3px solid var(--border);
  margin-bottom: 0.5rem;
}

/* ── Answer options ── */
.options { display: flex; flex-direction: column; gap: 0.55rem; }
.option {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  padding: 0.7rem 0.9rem;
  border: 1.5px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  background: var(--surface);
  transition: border-color 0.12s, background 0.12s;
  font-size: 0.95rem;
  user-select: none;
}
.option:hover { border-color: var(--primary); background: #f8faff; }
.option input[type=radio] { margin-top: 0.25rem; accent-color: var(--primary); flex-shrink: 0; }
.option.selected { border-color: var(--primary); background: var(--primary-light); font-weight: 500; }
.option.correct { border-color: var(--correct); background: #e6f4ea; }
.option.incorrect { border-color: var(--incorrect); background: #fce8e6; }

.actions { margin-top: 1.25rem; display: flex; gap: 0.75rem; align-items: center; }
.actions .btn { min-width: 100px; text-align: center; }
#submit-answer, #exam-submit { background: var(--primary); color: #fff; border-color: var(--primary); box-shadow: 0 2px 6px rgba(26,115,232,0.25); }
#submit-answer:hover, #exam-submit:hover { background: var(--primary-hover); }

/* ── Feedback ── */
.feedback-card { border-top: 3px solid var(--border); }
.feedback-card.correct-border { border-top-color: var(--correct); }
.feedback-card.incorrect-border { border-top-color: var(--incorrect); }
.correct-msg { color: var(--correct); font-weight: 700; font-size: 1rem; margin: 0 0 0.5rem; }
.incorrect-msg { color: var(--incorrect); font-weight: 700; font-size: 1rem; margin: 0 0 0.5rem; }
.solution { margin-top: 1rem; padding-top: 1rem; border-top: 1px solid var(--border); }
.solution .strategy { font-style: italic; color: var(--text-muted); margin-bottom: 0.5rem; font-size: 0.92rem; }
.solution .steps { margin: 0; padding-left: 1.25rem; }
.solution .steps li { margin-bottom: 0.3rem; font-size: 0.93rem; }
.solution .final { font-weight: 700; margin-top: 0.6rem; color: var(--primary); }

/* ── Exam ── */
.exam-setup h1 { margin-bottom: 0.5rem; }
.exam-setup label { display: flex; align-items: center; gap: 0.5rem; font-size: 0.9rem; margin: 1rem 0; cursor: pointer; }
.exam-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
  font-size: 0.88rem;
  color: var(--text-muted);
  font-weight: 500;
}
#exam-timer-display {
  font-variant-numeric: tabular-nums;
  background: #1c2b4a;
  color: #fff;
  padding: 0.25em 0.6em;
  border-radius: 5px;
  font-size: 0.85rem;
}

.exam-results h2 { margin-top: 0; }
.missed-types { margin: 1rem 0; display: flex; flex-wrap: wrap; gap: 0.4rem; }
.missed-types a {
  display: inline-block;
  padding: 0.3em 0.65em;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.82rem;
  color: var(--primary);
  text-decoration: none;
}
.missed-types a:hover { border-color: var(--primary); background: var(--primary-light); }

/* ── Loading ── */
#screen-loading { text-align: center; padding: 4rem; color: var(--text-muted); }

/* ── Responsive ── */
@media (max-width: 540px) {
  .main { padding: 1rem; }
  .type-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); }
  .header { padding: 0 1rem; }
}

/* ── Practice progress bar (visual) ── */
.practice-progress-bar-wrap {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1rem;
}
.practice-pbar-track {
  flex: 1;
  height: 6px;
  background: var(--border);
  border-radius: 99px;
  overflow: hidden;
}
.practice-pbar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), #34d399);
  border-radius: 99px;
  transition: width 0.4s ease;
  min-width: 0;
}
.practice-progress-label {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-weight: 600;
  white-space: nowrap;
  letter-spacing: 0.02em;
}

/* ── Smooth question transitions ── */
.question-card, .feedback-card {
  animation: fadeSlideIn 0.22s ease both;
}
@keyframes fadeSlideIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}