/* ===== Design Tokens ===== */
:root {
  --navy: #0b1120;
  --navy-light: #1a2744;
  --slate: #1e293b;
  --slate-light: #334155;
  --teal: #06d6a0;
  --teal-dark: #05b88a;
  --coral: #ef476f;
  --amber: #ffd166;
  --blue: #118ab2;
  --blue-dark: #0e7490;
  --bg: #f1f5f9;
  --surface: #ffffff;
  --surface-hover: #f8fafc;
  --text: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --radius: 10px;
  --radius-sm: 6px;
  --shadow: 0 1px 3px rgba(0,0,0,.06), 0 1px 2px rgba(0,0,0,.04);
  --shadow-lg: 0 4px 12px rgba(0,0,0,.08);
  --font: 'Inter', system-ui, -apple-system, sans-serif;
  --mono: 'JetBrains Mono', monospace;
}

/* ===== Reset ===== */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

/* ===== Base ===== */
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Top Bar ===== */
.topbar {
  background: var(--navy);
  position: sticky;
  top: 0;
  z-index: 100;
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.topbar::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 15% 50%, rgba(6,214,160,.06) 0%, transparent 60%),
    radial-gradient(circle at 85% 30%, rgba(17,138,178,.06) 0%, transparent 60%);
  pointer-events: none;
}
.topbar-inner {
  width: 100%;
  padding: 14px 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  position: relative;
}
.topbar-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: #fff;
}
.brand-icon {
  font-size: 1.6rem;
  color: var(--teal);
  line-height: 1;
}
.topbar-brand h1 {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -.01em;
  line-height: 1.2;
}
.brand-sub {
  font-size: .7rem;
  color: rgba(255,255,255,.5);
  text-transform: uppercase;
  letter-spacing: .08em;
}
.topbar-stats {
  font-size: .78rem;
  color: rgba(255,255,255,.5);
  font-family: var(--mono);
  white-space: nowrap;
}

/* ===== Main Layout ===== */
.main-layout {
  width: 100%;
  margin: 0;
  display: flex;
  gap: 0;
  min-height: calc(100vh - 62px);
}

/* ===== Content Area ===== */
.content-area {
  flex: 1;
  min-width: 0;
}
.content-wrapper {
  max-width: 1150px;
  margin: 0 auto;
  padding: 20px 24px 100px;
}



/* ===== Quiz Container ===== */
.quiz-container { display: flex; flex-direction: column; gap: 14px; }

/* ===== Question Cards ===== */
.q-card {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 18px 22px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  border-left: 4px solid var(--border);
  transition: border-color .2s, box-shadow .2s;
  position: relative;
}
.q-card::before {
  content: '';
  position: absolute;
  top: 20px;
  left: -4px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--border);
  border: 2px solid var(--surface);
  transition: background .2s;
}
.q-card.correct {
  border-left-color: var(--teal);
  box-shadow: 0 1px 4px rgba(6,214,160,.1);
}
.q-card.correct::before { background: var(--teal); }
.q-card.wrong {
  border-left-color: var(--coral);
  box-shadow: 0 1px 4px rgba(239,71,111,.1);
}
.q-card.wrong::before { background: var(--coral); }
.q-card.answered {
  border-left-color: var(--amber);
}
.q-card.answered::before { background: var(--amber); }

/* ===== Question Header ===== */
.q-num {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
  font-size: .78rem;
  font-weight: 600;
  letter-spacing: .01em;
}
.q-pts {
  font-weight: 500;
  font-size: .7rem;
  background: var(--bg);
  color: var(--text-secondary);
  padding: 1px 10px;
  border-radius: 8px;
  font-family: var(--mono);
}

/* ===== Question Text ===== */
.q-text {
  font-size: .92rem;
  margin-bottom: 14px;
  line-height: 1.7;
  color: var(--text);
}
.q-text .blank {
  display: inline-block;
  min-width: 70px;
  border-bottom: 2px dashed var(--blue);
  margin: 0 2px;
  padding: 0 4px;
  color: var(--blue);
  font-weight: 600;
  font-family: var(--mono);
  font-size: .82rem;
  text-align: center;
}

/* ===== Markdown Elements ===== */
.md-content { width: 100%; }
.md-content p, .q-text p { margin-bottom: 8px; }
.md-content p:last-child, .q-text p:last-child { margin-bottom: 0; }
.md-content table, .q-text table {
  border-collapse: collapse;
  width: 100%;
  margin: 12px 0;
  font-size: .85rem;
}
.md-content th, .md-content td, .q-text th, .q-text td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}
.md-content th, .q-text th {
  background: rgba(0,0,0,.03);
  font-weight: 600;
}
.md-content strong, .q-text strong { color: var(--navy); font-weight: 600; }
.md-content code, .q-text code, .opt-text code {
  font-family: var(--mono);
  background: rgba(0,0,0,.05);
  padding: 2px 4px;
  border-radius: 4px;
  font-size: .9em;
}
.opt-text { flex: 1; }
.opt-text p { margin: 0; display: inline; }
.options { display: flex; flex-direction: column; gap: 6px; }
.options label {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 9px 14px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: .88rem;
  border: 1px solid var(--border);
  transition: all .15s;
  background: var(--surface);
}
.options label:hover { background: var(--surface-hover); border-color: var(--slate-light); }
.options input[type="radio"], .options input[type="checkbox"] {
  margin-top: 3px;
  accent-color: var(--blue);
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}
.options label.correct-answer {
  background: rgba(6,214,160,.08);
  border-color: var(--teal);
}
.options label.wrong-answer {
  background: rgba(239,71,111,.08);
  border-color: var(--coral);
}
.options label.missed-answer {
  background: rgba(255,209,102,.1);
  border-color: var(--amber);
}

/* ===== Fill Inputs ===== */
.fill-input {
  width: 100%;
  padding: 9px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .88rem;
  font-family: var(--mono);
  margin-bottom: 4px;
  transition: border-color .2s, box-shadow .2s;
}
.fill-input:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(17,138,178,.1);
}
.fill-input.correct { border-color: var(--teal); background: rgba(6,214,160,.05); }
.fill-input.wrong { border-color: var(--coral); background: rgba(239,71,111,.05); }


/* ===== Short Answer ===== */
.short-textarea {
  width: 100%;
  min-height: 90px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .88rem;
  font-family: var(--font);
  resize: vertical;
  transition: border-color .2s, box-shadow .2s;
}
.short-textarea:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(17,138,178,.1);
}
.short-answer {
  margin-top: 10px;
  padding: 12px 14px;
  background: var(--bg);
  border-radius: var(--radius-sm);
  font-size: .84rem;
  line-height: 1.7;
  white-space: pre-wrap;
  display: none;
  border: 1px solid var(--border);
}
.short-answer.show { display: block; }
.short-answer .label {
  font-weight: 600;
  color: var(--teal-dark);
  display: block;
  margin-bottom: 4px;
}
.self-score-wrap {
  margin-top: 10px;
  display: none;
  align-items: center;
  gap: 8px;
  font-size: .85rem;
}
.self-score-wrap.show { display: flex; }
.self-score {
  width: 72px;
  padding: 5px 8px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .88rem;
  font-family: var(--mono);
  text-align: center;
}
.self-score:focus {
  outline: none;
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(17,138,178,.1);
}

/* ===== Feedback ===== */
.answer-feedback {
  margin-top: 10px;
  font-size: .82rem;
  font-weight: 500;
  display: none;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
}
.answer-feedback.show { display: block; }
.answer-feedback.correct {
  color: var(--teal-dark);
  background: rgba(6,214,160,.06);
}
.answer-feedback.wrong {
  color: var(--coral);
  background: rgba(239,71,111,.06);
}
.answer-feedback.answered {
  color: #b8860b;
  background: rgba(255,209,102,.08);
}

/* ===== Nav Panel ===== */
.nav-panel {
  width: 260px;
  flex-shrink: 0;
  background: var(--navy);
  position: sticky;
  top: 62px;
  height: calc(100vh - 62px);
  display: flex;
  flex-direction: column;
}

/* Nav: Mode Toggle */
.nav-toggle {
  display: flex;
  gap: 2px;
  padding: 12px 12px 8px;
  background: rgba(0,0,0,.15);
}
.nav-toggle .mode-btn {
  flex: 1;
  padding: 7px 8px;
  border: none;
  border-radius: 5px;
  font-size: .78rem;
  font-weight: 500;
  font-family: var(--font);
  cursor: pointer;
  transition: all .2s;
  background: transparent;
  color: rgba(255,255,255,.4);
  text-align: center;
}
.nav-toggle .mode-btn:hover { color: rgba(255,255,255,.7); }
.nav-toggle .mode-btn.active {
  background: var(--teal);
  color: #fff;
  box-shadow: 0 1px 4px rgba(6,214,160,.25);
}

/* Nav: Header */
.nav-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px 10px;
  padding: 10px 14px;
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.nav-title {
  color: #fff;
  font-size: .8rem;
  font-weight: 600;
}
.nav-collapse-btn {
  display: none;
  background: none;
  border: none;
  color: rgba(255,255,255,.4);
  font-size: 1rem;
  cursor: pointer;
  padding: 0 2px;
  line-height: 1;
  transition: color .15s;
}
.nav-collapse-btn:hover { color: rgba(255,255,255,.7); }

.nav-progress {
  margin-left: auto;
  font-size: .72rem;
  font-family: var(--mono);
  color: var(--teal);
  font-weight: 500;
}
.nav-legend {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: .68rem;
  color: rgba(255,255,255,.35);
  width: 100%;
}
.legend-dot {
  display: inline-block;
  width: 7px;
  height: 7px;
  border-radius: 50%;
}
.legend-dot.done { background: var(--teal); }
.legend-dot.miss { background: rgba(255,255,255,.1); border: 1px solid rgba(255,255,255,.2); }

/* Nav: Body */
.nav-body {
  flex: 1;
  overflow-y: auto;
  padding: 10px 10px 8px;
}
.nav-body::-webkit-scrollbar { width: 4px; }
.nav-body::-webkit-scrollbar-track { background: transparent; }
.nav-body::-webkit-scrollbar-thumb { background: rgba(255,255,255,.1); border-radius: 2px; }

.nav-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 5px;
  margin-bottom: 6px;
}
.nav-section-label {
  grid-column: 1 / -1;
  font-size: .62rem;
  color: rgba(255,255,255,.25);
  text-transform: uppercase;
  letter-spacing: .06em;
  padding-top: 6px;
  padding-bottom: 1px;
  border-top: 1px solid rgba(255,255,255,.06);
  margin-top: 2px;
}
.nav-section-label:first-child { border-top: none; margin-top: 0; padding-top: 0; }

.nav-btn {
  width: 100%;
  aspect-ratio: 1;
  border: 1px solid rgba(255,255,255,.1);
  border-radius: 5px;
  background: transparent;
  color: rgba(255,255,255,.35);
  font-size: .7rem;
  font-weight: 500;
  font-family: var(--mono);
  cursor: pointer;
  transition: all .15s;
  display: flex;
  align-items: center;
  justify-content: center;
}
.nav-btn:hover {
  background: rgba(255,255,255,.06);
  color: rgba(255,255,255,.65);
}
.nav-btn.done {
  background: rgba(6,214,160,.7);
  border-color: rgba(6,214,160,.8);
  color: #fff;
}
.nav-btn.current {
  border-color: #fff;
  color: #fff;
  box-shadow: 0 0 0 1.5px #fff;
}
.nav-btn.wrong {
  background: rgba(239,71,111,.4);
  border-color: rgba(239,71,111,.5);
  color: rgba(255,255,255,.6);
}
.nav-btn.partial {
  background: rgba(255,209,102,.75);
  border-color: rgba(255,209,102,.85);
  color: var(--navy);
}
.nav-btn.wrong-unanswered {
  background: rgba(255,209,102,.75);
  border-color: rgba(255,209,102,.85);
  color: var(--navy);
}

/* Nav: Action Buttons */
.nav-actions {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 10px 12px 14px;
  border-top: 1px solid rgba(255,255,255,.06);
  background: rgba(0,0,0,.08);
}
.nav-action-btn {
  display: block;
  width: 100%;
  padding: 9px 12px;
  border: 1px solid rgba(255,255,255,.12);
  border-radius: 6px;
  font-size: .8rem;
  font-weight: 500;
  font-family: var(--font);
  cursor: pointer;
  transition: all .15s;
  background: transparent;
  color: rgba(255,255,255,.5);
  text-align: center;
}
.nav-action-btn:hover {
  background: rgba(255,255,255,.06);
  color: rgba(255,255,255,.75);
}
.nav-action-btn.primary {
  background: var(--teal);
  border-color: var(--teal);
  color: #fff;
  font-weight: 600;
}
.nav-action-btn.primary:hover {
  background: var(--teal-dark);
  border-color: var(--teal-dark);
}
.nav-action-btn.accent {
  border-color: rgba(17,138,178,.4);
  color: rgba(17,138,178,.7);
}
.nav-action-btn.accent:hover {
  background: rgba(17,138,178,.12);
  border-color: rgba(17,138,178,.6);
  color: rgba(17,138,178,.9);
}

/* ===== Result Bar ===== */
.result-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 260px;
  background: var(--surface);
  border-top: 1px solid var(--border);
  box-shadow: 0 -4px 20px rgba(0,0,0,.08);
  display: none;
  z-index: 200;
}
.result-bar.show { display: block; }
.result-inner {
  max-width: 1150px;
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
}
.score {
  font-size: 1.05rem;
  font-weight: 700;
}
.score.good { color: var(--teal-dark); }
.score.ok { color: var(--amber); }
.score.bad { color: var(--coral); }
.detail {
  font-size: .8rem;
  color: var(--text-secondary);
  font-family: var(--mono);
}

/* ===== Scrollbar Global ===== */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* ===== KaTeX overflow fix ===== */
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.katex { font-size: 1.05em; }

/* ===== Responsive ===== */
@media (max-width: 1024px) {
  .nav-panel { width: 220px; }
  .result-bar { right: 220px; }
  .nav-grid { grid-template-columns: repeat(4, 1fr); }
}

@media (max-width: 768px) {
  /* Layout collapse */
  .main-layout { flex-direction: column; min-height: auto; }
  .content-wrapper { padding: 12px 12px 0; max-width: 100%; }
  
  /* Topbar compact */
  .topbar-inner { padding: 10px 14px; gap: 6px; }
  .topbar-brand { gap: 8px; }
  .topbar-brand h1 { font-size: .95rem; }
  .brand-icon { font-size: 1.2rem; }
  .brand-sub { display: none; }
  .topbar-stats { font-size: .62rem; white-space: normal; line-height: 1.4; text-align: right; }
  
  /* Cards compact */
  .q-card { padding: 12px 14px; border-radius: 8px; }
  .q-card::before { top: 15px; width: 8px; height: 8px; left: -3px; }
  .q-text { font-size: .85rem; }
  .q-text .blank { min-width: 50px; font-size: .78rem; }
  
  /* Options compact */
  .options label { padding: 8px 10px; font-size: .82rem; gap: 8px; }
  .options input[type="radio"], .options input[type="checkbox"] { width: 14px; height: 14px; }
  
  /* Fill inputs */
  .fill-input { padding: 7px 10px; font-size: .82rem; }
  .short-textarea { min-height: 70px; font-size: .82rem; padding: 8px 10px; }
  
  /* Nav to bottom drawer */
  .nav-panel {
    position: fixed;
    left: 0;
    right: 0;
    top: auto;
    bottom: 0;
    width: 100%;
    height: 50vh;
    z-index: 150;
    border-top: 1px solid rgba(255,255,255,.1);
    border-radius: 12px 12px 0 0;
    touch-action: none;
    will-change: transform;
  }
  
  /* Drag handle visual */
  .nav-panel::before {
    content: '';
    display: block;
    width: 36px;
    height: 4px;
    border-radius: 2px;
    background: rgba(255,255,255,.15);
    margin: 0 auto;
    position: absolute;
    top: -8px;
    left: 50%;
    transform: translateX(-50%);
  }
  
  .nav-toggle { padding: 10px 12px 6px; }
  .nav-toggle .mode-btn { padding: 5px 6px; font-size: .72rem; }
  
  .nav-header { padding: 6px 12px; }
  .nav-title { font-size: .72rem; }
  .nav-collapse-btn { display: inline-block; font-size: .85rem; margin-left: auto; }
  .nav-progress { font-size: .65rem; }
  .nav-legend { font-size: .6rem; gap: 5px; }
  .legend-dot { width: 6px; height: 6px; }
  
  .nav-body { 
    max-height: calc(50vh - 120px); 
    padding: 6px 10px; 
    overflow-y: auto;
  }
  .nav-grid { 
    grid-template-columns: repeat(10, 1fr); 
    gap: 3px; 
    margin-bottom: 3px;
  }
  .nav-section-label { font-size: .55rem; padding-top: 3px; }
  .nav-btn { font-size: .58rem; border-radius: 3px; }
  
  .nav-actions { 
    flex-direction: row; 
    flex-wrap: wrap;
    padding: 6px 10px 10px;
    gap: 5px;
  }
  .nav-action-btn {
    flex: 1;
    min-width: 70px;
    padding: 7px 6px;
    font-size: .72rem;
  }
  
  .result-bar { left: 0; right: 0; }
  .result-bar.in-nav { position: static; box-shadow: none; border-top: 1px solid rgba(255,255,255,.06); background: rgba(0,0,0,.08); }
  .result-inner { padding: 10px 14px; gap: 8px; flex-direction: column; text-align: center; }
  .score { font-size: .9rem; }
  .detail { font-size: .7rem; }
  
  /* Bottom spacing for fixed nav */
  .quiz-container { padding-bottom: calc(50vh + 60px); }
}

@media (max-width: 480px) {
  .topbar-stats { font-size: .55rem; }
  .q-card { padding: 10px 12px; }
  .q-text { font-size: .8rem; }
  .q-num { font-size: .7rem; gap: 6px; }
  .q-pts { font-size: .62rem; padding: 0 7px; }
  
  .nav-grid { grid-template-columns: repeat(8, 1fr); gap: 2px; }
  .nav-btn { font-size: .52rem; border-radius: 2px; }
  .nav-action-btn { min-width: 60px; padding: 6px 4px; font-size: .68rem; }
  
  .options label { padding: 6px 8px; font-size: .78rem; }
  .fill-input { padding: 6px 8px; font-size: .78rem; }
  .short-textarea { min-height: 60px; font-size: .78rem; }
  
  .answer-feedback { font-size: .75rem; padding: 4px 8px; }
  .short-answer { font-size: .78rem; padding: 8px 10px; }
  
  .result-inner { padding: 8px 10px; }
  .score { font-size: .82rem; }
}