:root {
  --bg: #FFFFFF;
  --card: #F2F3F3;
  --card-hi: #E7E9EA;
  --card-dim: #FAFAFA;
  --text: #16191F;
  --text-dim: #5F6B7A;
  --border: #D5DBDB;

  --orange: #FF9900;
  --blue: #0972D3;
  --purple: #6D28D9;
  --teal: #0F766E;
  --pink: #BE185D;

  --ok: #1D8102;
  --ok-ink: #FFFFFF;
  --bad: #D13212;
  --bad-ink: #FFFFFF;
  --accent: #B3530C;
  --warn: #92720C;

  --mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --sans: 'Quicksand', -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
}

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem 3rem;
}

nav {
  display: flex;
  gap: 1.75rem;
  max-width: 900px;
  margin: 0 auto;
  padding: 1.5rem 2rem 1rem;
  border-bottom: 1px solid var(--border);
}

.nav-btn {
  background: none;
  border: none;
  padding: 0 0 0.5rem;
  font: 700 0.9rem var(--mono);
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--text-dim);
  border-bottom: 2px solid transparent;
  cursor: pointer;
}

.nav-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.stats-bar {
  display: flex;
  gap: 1.5rem;
  max-width: 900px;
  margin: 0 auto;
  padding: 0.75rem 2rem;
  font-size: 0.85rem;
  color: var(--text-dim);
  border-bottom: 1px solid var(--border);
}

.stats-bar strong { color: var(--accent); font-weight: 700; }

.view { display: none; padding-top: 1.5rem; }
.view.active { display: block; }

.meta-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.meta-label {
  font: 0.85rem var(--mono);
  color: var(--text-dim);
  letter-spacing: 0.02em;
}

.question-text {
  margin: 0 0 1rem;
  font-size: 1.4rem;
  line-height: 1.5;
  font-weight: 700;
  color: var(--text);
}

.badge-multi {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--card);
  color: var(--text-dim);
  padding: 0.3rem 0.7rem;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

/* --- Review tabs (toggle between your answer and the explanation) --- */
.review-tabs { display: flex; gap: 8px; margin-bottom: 1rem; }
.review-tabs[hidden] { display: none; }
.tab {
  background: var(--card);
  color: var(--text-dim);
  border: 1.5px solid var(--border);
  border-radius: 999px;
  padding: 0.55rem 1.1rem;
  font: 700 0.88rem var(--sans);
  cursor: pointer;
  transition: background 0.15s ease;
}
.tab:hover:not(.active) { background: var(--card-hi); }
.tab.active { background: var(--accent); color: #fff; border-color: var(--accent); }

/* --- Options list (Quiz/Review interactive buttons, Flashcard static rows) --- */
.list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 0 0 1rem;
}

.hide { display: none; }

.opt {
  position: relative;
  display: flex;
  align-items: center;
  gap: 0.9rem;
  text-align: left;
  width: 100%;
  background: var(--card);
  border-radius: 20px;
  padding: 1rem 1.1rem;
  font: 600 1rem var(--sans);
  color: var(--text);
  line-height: 1.4;
  border: 1.5px solid var(--border);
  box-shadow: 0 1px 2px rgba(22, 25, 31, 0.05);
}

button.opt {
  cursor: pointer;
  transition: transform 0.12s ease, background 0.2s ease, border-color 0.2s ease;
}
button.opt:hover:not(:disabled) { transform: translateX(4px); background: var(--card-hi); }
button.opt:focus-visible { outline: none; border-color: var(--accent); box-shadow: 0 0 0 4px rgba(179, 83, 12, 0.22); }
button.opt:disabled { cursor: default; }

.badge {
  flex: none;
  width: 2.1rem;
  height: 2.1rem;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 1rem;
  color: var(--text);
}
.opt[data-letter="A"] .badge { background: var(--orange); }
.opt[data-letter="B"] .badge { background: var(--blue); color: #fff; }
.opt[data-letter="C"] .badge { background: var(--purple); color: #fff; }
.opt[data-letter="D"] .badge { background: var(--teal); color: #fff; }
.opt[data-letter="E"] .badge { background: var(--pink); color: #fff; }

.opt-text { flex: 1; }
.icon { flex: none; width: 1.5rem; height: 1.5rem; display: none; }

/* multi-select: toggled-but-not-locked state */
.opt.selected { background: #FFF4EA; border-color: var(--accent); }
.opt.selected .badge { box-shadow: 0 0 0 3px rgba(179, 83, 12, 0.3); }

/* locked/revealed states */
.opt.correct { background: var(--ok); color: var(--ok-ink); border-color: var(--ok); animation: pop-correct 0.4s ease; }
.opt.correct .badge { background: rgba(0, 0, 0, 0.2); color: #fff; }
.opt.correct .icon.check { display: block; }

.opt.incorrect { background: var(--bad); color: var(--bad-ink); border-color: var(--bad); }
.opt.incorrect .badge { background: rgba(0, 0, 0, 0.2); color: #fff; }
.opt.incorrect .icon.cross { display: block; }

.opt.missed { background: var(--card-dim); border: 2px dashed var(--ok); color: var(--ok); }
.opt.missed .icon.check { display: block; opacity: 0.8; }

.opt.neutral { opacity: 0.45; }

@keyframes pop-correct { 0% { transform: scale(1); } 40% { transform: scale(1.03); } 100% { transform: scale(1); } }

/* Flashcards: same visual language, non-interactive */
.flash-options .opt { cursor: default; }

/* --- Submit / CTA buttons --- */
.submit-row { margin-top: 0.25rem; display: flex; justify-content: flex-end; }
.submit-row.hide { display: none; }
.submit {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 999px;
  padding: 0.85rem 2rem;
  font: 700 1rem var(--sans);
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
}
.submit.ready { opacity: 1; pointer-events: auto; }
.submit:disabled { background: var(--border); color: var(--text-dim); cursor: not-allowed; }

button {
  cursor: pointer;
  font-family: var(--sans);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  border: none;
  font: 700 0.95rem var(--sans);
  padding: 0.75rem 1.75rem;
  border-radius: 999px;
}

.btn-primary:disabled {
  background: var(--border);
  color: var(--text-dim);
  cursor: not-allowed;
}

.btn-ghost {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-dim);
  font: 0.8rem var(--mono);
  letter-spacing: 0.02em;
  text-transform: uppercase;
  padding: 0.4rem 0.75rem;
  border-radius: 999px;
}

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

/* --- Explanation panel: recap chips, disputed chip, verdict, body --- */
.explain-panel {
  display: none;
  background: var(--card-dim);
  border-radius: 24px;
  padding: 1.75rem;
  border: 1.5px solid var(--border);
  border-top: 5px solid var(--accent);
}
.explain-panel.show { display: block; animation: pop 0.3s ease; }
@keyframes pop { from { opacity: 0; transform: scale(0.94); } to { opacity: 1; transform: scale(1); } }

.recap { display: flex; flex-wrap: wrap; gap: 0.6rem; margin-bottom: 1rem; }
.recap span { font-size: 0.82rem; font-weight: 700; padding: 0.4rem 0.75rem; border-radius: 999px; }
.recap .you { background: var(--card); color: var(--text-dim); }
.recap .you.wrong { background: #FCEAE6; color: #9A2A16; }
.recap .correct-pill { background: #E8F4E3; color: #175E02; }

.disputed-chip {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--warn);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 800;
  padding: 0.4rem 0.8rem;
  border-radius: 999px;
  margin-bottom: 1rem;
}

.verdict { font-size: 1.3rem; font-weight: 800; margin: 0 0 0.75rem; }
.verdict.correct, .verdict.ok { color: var(--ok); }
.verdict.incorrect, .verdict.bad { color: var(--bad); }

.explanation {
  color: var(--text-dim);
  font-size: 0.92rem;
  line-height: 1.65;
  margin: 0;
  font-weight: 500;
}

.actions { display: flex; justify-content: space-between; align-items: center; margin-top: 1.25rem; }
.actions[hidden] { display: none; }

.done-note { color: var(--text-dim); font-weight: 700; font-size: 0.95rem; }

.flash-actions {
  margin-top: 1.5rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

/* Mobile: tighter padding, smaller type, wrapping rows, larger tap targets */
@media (max-width: 640px) {
  nav {
    gap: 1rem;
    padding: 1rem 1.25rem 0.75rem;
    flex-wrap: wrap;
  }

  .nav-btn {
    font-size: 0.75rem;
  }

  main {
    padding: 0 1.25rem 2rem;
  }

  .stats-bar {
    padding: 0.6rem 1.25rem;
    gap: 1rem;
    flex-wrap: wrap;
    font-size: 0.8rem;
  }

  .question-text {
    font-size: 1.15rem;
    line-height: 1.45;
  }

  .opt {
    padding: 0.9rem 0.85rem;
    font-size: 0.92rem;
    gap: 0.6rem;
  }

  .btn-primary, .btn-ghost, .submit {
    padding: 0.85rem 1.5rem;
  }

  .explain-panel {
    padding: 1.25rem;
  }
}