/* ─── MCQ & Practice Pages ───────────────────────────────────────────────── */

/* Chapter switcher nav (underline style) */
.ch-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(253, 252, 250, .94);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--sand-200);
  padding: .5rem 0;
  overflow-x: auto;
}
.ch-nav::-webkit-scrollbar { display: none }
.ch-nav-inner {
  display: flex;
  gap: 0;
  max-width: 80%;
  margin: 0 auto;
  padding: 0 1.25rem;
  min-width: max-content;
}
.ch-btn {
  padding: .4rem 1rem;
  font-size: .75rem;
  font-weight: 700;
  border: none;
  background: none;
  cursor: pointer;
  color: var(--ink-3);
  border-bottom: 2.5px solid transparent;
  transition: all .18s;
  white-space: nowrap;
  font-family: 'Lato', sans-serif;
}
.ch-btn:hover  { color: var(--ink) }
.ch-btn.active { color: var(--ink); border-bottom-color: var(--sand-900) }

/* Chapter panel */
.ch-panel { display: none; padding: 2rem 0 3rem }
.ch-panel.active { display: block }

/* Chapter heading inside panel */
.ch-heading {
  font-family: 'Newsreader', serif;
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--ink);
  margin-bottom: 1.25rem;
  padding-bottom: .6rem;
  border-bottom: 1px solid var(--sand-200);
  display: flex;
  align-items: center;
  gap: .6rem;
}
.ch-mark-badge {
  font-size: .68rem;
  font-weight: 700;
  border-radius: 999px;
  padding: .2rem .65rem;
  color: #fff;
}

/* Score bar */
.score-bar {
  display: flex;
  align-items: center;
  gap: 1rem;
  background: #fff;
  border: 1px solid var(--sand-200);
  border-radius: 10px;
  padding: .75rem 1.25rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}
.score-label {
  font-size: .72rem;
  font-weight: 700;
  color: var(--ink-3);
  text-transform: uppercase;
  letter-spacing: .04em;
}
.score-val {
  font-family: 'Newsreader', serif;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--ink);
}
.score-progress {
  flex: 1;
  height: 6px;
  background: var(--sand-200);
  border-radius: 999px;
  overflow: hidden;
  min-width: 80px;
}
.score-fill {
  height: 100%;
  background: var(--sand-900);
  border-radius: 999px;
  transition: width .3s;
}
.reset-btn {
  font-size: .68rem;
  font-weight: 700;
  color: var(--ink-3);
  background: var(--sand-100);
  border: 1px solid var(--sand-200);
  border-radius: 6px;
  padding: .3rem .7rem;
  cursor: pointer;
  font-family: 'Lato', sans-serif;
}
.reset-btn:hover { color: var(--ink); background: var(--sand-200) }

/* MCQ card */
.mcq-card {
  background: #fff;
  border: 1px solid var(--sand-200);
  border-radius: 12px;
  padding: 1.25rem;
  margin-bottom: 1rem;
  transition: box-shadow .2s;
}
.mcq-card:hover { box-shadow: 0 4px 16px rgba(0,0,0,.06) }

.mcq-num {
  font-size: .65rem;
  font-weight: 800;
  color: var(--ink-3);
  text-transform: uppercase;
  letter-spacing: .06em;
  margin-bottom: .5rem;
}
.mcq-q {
  font-size: .88rem;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.5;
  margin-bottom: .9rem;
}
.mcq-opts {
  display: flex;
  flex-direction: column;
  gap: .4rem;
}

/* Option button */
.opt {
  display: flex;
  align-items: flex-start;
  gap: .6rem;
  padding: .55rem .8rem;
  border-radius: 8px;
  border: 1.5px solid var(--sand-200);
  background: var(--sand-50);
  cursor: pointer;
  font-size: .8rem;
  color: var(--ink-2);
  text-align: left;
  transition: all .15s;
  font-family: 'Lato', sans-serif;
  line-height: 1.4;
}
.opt:hover:not(:disabled) {
  border-color: var(--sand-300);
  background: var(--sand-100);
  color: var(--ink);
}
.opt:disabled { cursor: default }
.opt-letter {
  font-weight: 800;
  color: var(--ink-3);
  flex-shrink: 0;
  min-width: 16px;
}

/* Answer states */
.opt.correct              { background: #f0fdf4; border-color: #86efac; color: #166534 }
.opt.correct .opt-letter  { color: #16a34a }
.opt.wrong                { background: #fef2f2; border-color: #fca5a5; color: #991b1b }
.opt.wrong .opt-letter    { color: #dc2626 }

/* Explanation */
.mcq-exp {
  margin-top: .85rem;
  padding: .75rem 1rem;
  background: #f8fafc;
  border-left: 3px solid var(--sand-300);
  border-radius: 0 6px 6px 0;
  font-size: .76rem;
  color: var(--ink-2);
  line-height: 1.6;
  display: none;
}
.mcq-exp strong { color: var(--ink) }

/* ─── Chapter engine states ─────────────────────────────────────────────── */
.opt.selected { border-color: var(--subject-color, var(--sand-900)); background: var(--subject-bg, var(--sand-100)) }

.score-card { display: none; text-align: center; margin: 1rem 0 }
.score-card.show { display: block }
.score-big { font-family: 'Newsreader', serif; font-size: 3rem; font-weight: 700; color: var(--ink) }
.score-big.good { color: #16a34a }
.score-big.ok   { color: #d97706 }
.score-big.bad  { color: #dc2626 }

.nav-buttons, .bottom-bar { display: flex; align-items: center; justify-content: space-between; margin: 1rem 0; gap: .75rem }
.bottom-bar { justify-content: center }

.q-nav { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin-bottom: 1rem }

.section-label { font-size: .65rem; font-weight: 800; text-transform: uppercase; letter-spacing: .06em; color: var(--ink-3); width: 100%; margin-top: .5rem }

.concept-toc { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 1rem }
.concept-nav { display: flex; align-items: center; justify-content: space-between; margin: 1rem 0 2rem }

/* ─── Question navigation dots (shared) ─────────────────────────────────── */
.q-dot {
  min-width: 32px;
  height: 32px;
  padding: 0 8px;
  border-radius: 8px;
  border: 1.5px solid var(--sand-300);
  background: #fff;
  font-size: .72rem;
  font-weight: 700;
  color: var(--ink-2);
  cursor: pointer;
  transition: all .15s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: 'Lato', sans-serif;
}
.q-dot.active   { background: var(--sand-900); color: #fff; border-color: var(--sand-900) }
.q-dot.answered { background: #dbeafe; border-color: #93c5fd; color: #1d4ed8 }
.q-dot.correct  { background: #dcfce7; border-color: #86efac; color: #15803d }
.q-dot.wrong    { background: #fee2e2; border-color: #fca5a5; color: #991b1b }

/* ─── Case Study Page ─────────────────────────────────────────────────────── */

/* Top bar: score + progress + action buttons */
.top-bar {
  display: flex;
  align-items: center;
  gap: 1rem;
  background: #fff;
  border: 1px solid var(--sand-200);
  border-radius: 10px;
  padding: .75rem 1.25rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  position: sticky;
  top: 0;
  z-index: 50;
}
.score-display {
  font-size: .78rem;
  font-weight: 700;
  color: var(--ink-3);
  white-space: nowrap;
}
.score-display span { color: var(--ink); font-size: 1rem; font-family: 'Newsreader', serif }
.progress-wrap { flex: 1; min-width: 120px }
.progress-bar-bg {
  height: 6px;
  background: var(--sand-200);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: .2rem;
}
.progress-bar-fill {
  height: 100%;
  background: var(--subject-color, var(--sand-900));
  border-radius: 999px;
  transition: width .3s;
  width: 0%;
}
.progress-label {
  font-size: .65rem;
  color: var(--ink-3);
  font-weight: 600;
}

/* Action buttons */
.btn {
  font-size: .75rem;
  font-weight: 700;
  padding: .4rem .9rem;
  border-radius: 7px;
  border: 1.5px solid;
  cursor: pointer;
  font-family: 'Lato', sans-serif;
  transition: all .15s;
  white-space: nowrap;
}
.btn-test  { background: #fff; color: var(--ink-2); border-color: var(--sand-300) }
.btn-test:hover { background: var(--sand-100) }
.btn-test.active { background: var(--subject-color, var(--sand-900)); color: #fff; border-color: var(--subject-color, var(--sand-900)) }
.btn-submit { background: #dc2626; color: #fff; border-color: #dc2626 }
.btn-submit:hover { background: #b91c1c; border-color: #b91c1c }
.btn-reset { background: var(--sand-100); color: var(--ink-3); border-color: var(--sand-200) }
.btn-reset:hover { background: var(--sand-200); color: var(--ink) }

/* Case study card */
.case-study {
  background: #fff;
  border: 1px solid var(--sand-200);
  border-radius: 14px;
  overflow: hidden;
  margin-bottom: 2rem;
  box-shadow: 0 2px 8px rgba(0,0,0,.04);
}
.case-study-header {
  background: var(--subject-bg, var(--sand-100));
  border-bottom: 1px solid var(--subject-border, var(--sand-200));
  padding: .85rem 1.5rem;
}
.case-number {
  font-size: .65rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .06em;
  color: var(--subject-color, var(--sand-700));
  background: #fff;
  border: 1px solid var(--subject-border, var(--sand-300));
  border-radius: 999px;
  padding: .2rem .65rem;
}
.case-study h2 {
  font-family: 'Newsreader', serif;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--ink);
  padding: 1rem 1.5rem .5rem;
}
.passage {
  padding: .5rem 1.5rem 1.25rem;
  font-size: .85rem;
  color: var(--ink-2);
  line-height: 1.85;
  border-bottom: 1px solid var(--sand-100);
}

/* Question block */
.question-block {
  padding: 1.1rem 1.5rem;
  border-top: 1px solid var(--sand-100);
}
.q-label {
  font-size: .68rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .05em;
  color: var(--subject-color, var(--sand-700));
  margin-bottom: .35rem;
}
.q-text {
  font-size: .88rem;
  color: var(--ink);
  line-height: 1.55;
  margin-bottom: .75rem;
}

/* Options list */
.options {
  list-style: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: .35rem;
  margin-bottom: .75rem;
}
.options li {
  padding: .5rem .85rem;
  border-radius: 8px;
  border: 1.5px solid var(--sand-200);
  background: var(--sand-50);
  font-size: .82rem;
  color: var(--ink-2);
  cursor: pointer;
  transition: all .15s;
}
.options li:hover { border-color: var(--sand-300); background: var(--sand-100); color: var(--ink) }
.options li.selected { border-color: var(--subject-color, var(--sand-900)); background: var(--subject-bg, var(--sand-100)); color: var(--ink) }
.options li.correct-answer { background: #f0fdf4; border-color: #86efac; color: #166534 }
.options li.wrong-answer   { background: #fef2f2; border-color: #fca5a5; color: #991b1b }
body.test-mode .show-answer-btn { display: none }

/* Show answer button */
.show-answer-btn {
  font-size: .7rem;
  font-weight: 700;
  color: var(--ink-3);
  background: var(--sand-100);
  border: 1px solid var(--sand-200);
  border-radius: 6px;
  padding: .3rem .75rem;
  cursor: pointer;
  font-family: 'Lato', sans-serif;
  transition: all .15s;
  margin-bottom: .5rem;
}
.show-answer-btn:hover { background: var(--sand-200); color: var(--ink) }

/* Answer reveal box */
.answer-box {
  display: none;
  background: var(--sand-50);
  border: 1px solid var(--sand-200);
  border-radius: 8px;
  padding: .85rem 1rem;
  font-family: "Source Serif 4", Georgia, serif;
  font-size: .92rem;
  color: var(--ink-2);
  line-height: 1.75;
  margin-top: .25rem;
}
.answer-box.visible { display: block }
.ans-label {
  font-weight: 800;
  color: var(--subject-color, var(--sand-900));
  display: block;
  margin-bottom: .3rem;
}

/* Results overlay */
.results-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.45);
  z-index: 200;
  align-items: center;
  justify-content: center;
}
.results-overlay.visible { display: flex }
.results-card {
  background: #fff;
  border-radius: 16px;
  padding: 2rem 2.5rem;
  text-align: center;
  max-width: 400px;
  width: 90%;
  box-shadow: 0 12px 40px rgba(0,0,0,.18);
}
.results-card h2 {
  font-family: 'Newsreader', serif;
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--ink);
  margin-bottom: .75rem;
}
.results-score {
  font-family: 'Newsreader', serif;
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--subject-color, var(--sand-900));
  margin-bottom: .5rem;
}
.results-card p {
  font-size: .84rem;
  color: var(--ink-2);
  line-height: 1.6;
  margin-bottom: 1.25rem;
}
.results-card .btn { margin: .25rem }

/* ─── Mobile ─────────────────────────────────────────────────────────────── */
@media (max-width: 640px) {
  /* Replace chapter nav tabs with dropdown */
  .ch-nav-inner { display: none; }
  .ch-nav .mobile-select { display: block; margin: 0 auto; max-width: 95%; }
  .ch-nav { padding: .4rem .5rem; }

  /* Replace question dots with dropdown */
  .q-nav .q-dot, .q-nav .section-label { display: none; }
  .q-nav .mobile-select { display: block; }

  /* Compact chapter heading */
  .ch-heading { font-size: 1rem; margin-bottom: .85rem; }

  /* Compact score bar */
  .score-bar { padding: .5rem .75rem; gap: .6rem; margin-bottom: 1rem; border-radius: 8px; }
  .score-val { font-size: 1rem; }

  /* Compact MCQ cards */
  .mcq-card { padding: .85rem; border-radius: 10px; margin-bottom: .75rem; }
  .mcq-q { font-size: .82rem; margin-bottom: .65rem; }
  .opt { padding: .45rem .65rem; font-size: .75rem; border-radius: 7px; }
  .mcq-exp { padding: .6rem .75rem; font-size: .72rem; }

  /* Compact question dots */
  .q-dot { min-width: 28px; height: 28px; font-size: .65rem; border-radius: 6px; }

  /* Compact top bar (case study) */
  .top-bar { padding: .5rem .75rem; gap: .5rem; margin-bottom: 1rem; border-radius: 8px; }
  .score-display { font-size: .7rem; }
  .score-display span { font-size: .85rem; }

  /* Compact case study */
  .case-study { border-radius: 10px; margin-bottom: 1.25rem; }
  .case-study-header { padding: .6rem 1rem; }
  .case-study h2 { font-size: .95rem; padding: .75rem 1rem .35rem; }
  .passage { padding: .4rem 1rem 1rem; font-size: .78rem; }
  .question-block { padding: .85rem 1rem; }
  .q-text { font-size: .82rem; }
  .options li { padding: .4rem .7rem; font-size: .75rem; border-radius: 7px; }

  /* Results overlay */
  .results-card { padding: 1.5rem; border-radius: 14px; }
  .results-card h2 { font-size: 1.15rem; }
  .results-score { font-size: 2rem; }

  /* Buttons */
  .btn { font-size: .7rem; padding: .35rem .75rem; }
}