*, *::before, *::after { box-sizing: border-box; }

:root {
  --bg: #fafaf8;
  --surface: #ffffff;
  --ink: #1a1a1a;
  --muted: #6b6b6b;
  --line: #e2e2dc;
  --accent: #2d5a3d;
  --accent-soft: #e8f0ea;
  --correct: #2d5a3d;
  --correct-soft: #e8f0ea;
  --warn: #a6672a;
  --warn-soft: #f3e6d8;
  --max: 760px;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.55;
}

h1, h2 {
  font-weight: 600;
  text-wrap: balance;
  margin: 0;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.site-header, .site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 20px;
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 32px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--line);
  flex-wrap: wrap;
  gap: 10px;
}

.site-header .logo { font-size: 18px; font-weight: 600; letter-spacing: -0.3px; }
.site-header .logo a { color: var(--ink); }
.site-header .logo span { color: var(--muted); font-weight: 400; }

.site-header nav a { font-size: 15px; color: var(--muted); margin-left: 24px; text-decoration: none; }
.site-header nav a:hover { color: var(--ink); text-decoration: none; }

.site-footer {
  padding-top: 40px;
  padding-bottom: 40px;
  border-top: 1px solid var(--line);
  font-size: 0.85rem;
  color: var(--muted);
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: space-between;
  align-items: center;
}
.site-footer .support-link { color: var(--accent); text-decoration: none; }
.site-footer .support-link:hover { text-decoration: underline; }

.wrap {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 20px 72px;
}

@media (max-width: 480px) {
  .site-header nav a:first-child { margin-left: 0; }
  .site-footer { flex-direction: column; gap: 8px; text-align: center; }
}

header.quiz-header {
  padding: 40px 0 24px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 24px;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 10px;
}

.quiz-header h1 { font-size: 1.7rem; margin-bottom: 8px; }

.quiz-header .source {
  color: var(--muted);
  font-size: 0.88rem;
  margin: 0;
}

.back-link {
  display: inline-block;
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 18px;
  text-decoration: none;
}
.back-link:hover { color: var(--accent); text-decoration: underline; }

.quiz-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 18px;
  font-size: 0.85rem;
  color: var(--muted);
}

.reveal-all {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--accent);
  border-radius: 8px;
  padding: 8px 16px;
  cursor: pointer;
}
.reveal-all:hover { opacity: 0.85; }

.quiz-item {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 18px 20px;
  margin-bottom: 14px;
}

.q-stem {
  font-weight: 600;
  font-size: 0.98rem;
  margin-bottom: 12px;
}

.q-num {
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
  color: var(--accent);
  margin-right: 6px;
  font-weight: 700;
}

.q-options {
  list-style: none;
  margin: 0 0 14px;
  padding: 0;
  display: grid;
  gap: 6px;
}

.q-options li {
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-radius: 7px;
  font-size: 0.92rem;
  background: var(--bg);
}

.opt-letter {
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
  color: var(--muted);
  margin-right: 8px;
  font-weight: 700;
}

.quiz-item.revealed .q-options li.is-correct {
  background: var(--correct-soft);
  border-color: var(--correct);
  font-weight: 600;
}
.quiz-item.revealed .q-options li.is-correct .opt-letter { color: var(--correct); }

.reveal-btn {
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--accent);
  background: none;
  border: 1px solid var(--accent);
  border-radius: 7px;
  padding: 7px 14px;
  cursor: pointer;
}
.reveal-btn:hover { background: var(--accent-soft); }

.q-answer {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px dashed var(--line);
  font-size: 0.88rem;
  color: var(--ink);
}
.q-answer strong { color: var(--correct); }

.q-source {
  display: block;
  margin-top: 6px;
  font-size: 0.78rem;
  color: var(--muted);
}

.coverage-note {
  background: var(--warn-soft);
  border: 1px solid color-mix(in srgb, var(--warn) 35%, var(--line));
  border-radius: 8px;
  padding: 12px 16px;
  font-size: 0.85rem;
  margin-bottom: 24px;
  color: var(--ink);
}
.coverage-note strong { color: var(--warn); }

footer.quiz-footer {
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  font-size: 0.78rem;
  color: var(--muted);
}

@media (max-width: 480px) {
  .quiz-meta { flex-direction: column; align-items: flex-start; }
}

/* Lecture-deck emphasis flag and filter */
.deck-filter {
  font: inherit; font-size: 0.82rem; padding: 5px 12px; border-radius: 20px;
  border: 1px solid var(--border, #e2e2dc); background: #fff;
  color: var(--muted, #6b6b6b); cursor: pointer; margin-right: auto; margin-left: 12px;
}
.deck-filter:hover { border-color: var(--accent, #2d5a3d); color: var(--accent, #2d5a3d); }
.deck-filter.active {
  background: var(--accent-light, #e8f0ea); border-color: var(--accent, #2d5a3d);
  color: var(--accent, #2d5a3d); font-weight: 600;
}
.quiz-item.is-lecture { border-left: 3px solid var(--accent, #2d5a3d); }
.deck-flag {
  display: inline-block; margin-top: 10px; font-size: 0.68rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.05em;
  color: var(--accent, #2d5a3d); background: var(--accent-light, #e8f0ea);
  border-radius: 20px; padding: 2px 9px;
}