:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #0f172a;
  --muted: #475569;
  --primary: #2563eb;
  --primary-strong: #1d4ed8;
  --line: #e2e8f0;
  --radius: 12px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 15px;
  line-height: 1.58;
}

h1,
h2,
h3 {
  line-height: 1.35;
  margin: 0 0 0.6rem;
}

h1 {
  font-size: 1.28rem;
}

h2 {
  font-size: 1.05rem;
}

p {
  margin: 0 0 0.65rem;
}

a {
  color: var(--primary);
}

.container {
  width: min(100% - 1.25rem, 760px);
  margin-inline: auto;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: #ffffffeb;
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--line);
  margin-bottom: 0.9rem;
}

.nav-wrap {
  padding: 0.62rem 0;
}

.brand {
  display: inline-block;
  margin-bottom: 0.35rem;
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
  font-size: 0.96rem;
}

.nav-list {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.4rem;
  margin: 0;
  padding: 0;
  width: 100%;
}

.nav-list a {
  display: block;
  text-decoration: none;
  color: var(--text);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.42rem 0.7rem;
  min-height: 2.1rem;
  text-align: center;
  font-size: 0.88rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 0.82rem;
  margin-bottom: 0.62rem;
}

.hero {
  padding: 0.88rem;
}

.eyebrow {
  display: inline-block;
  margin-bottom: 0.45rem;
  padding: 0.15rem 0.55rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  font-size: 0.86rem;
}

.filter-row {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  margin-top: 0.45rem;
  flex-wrap: wrap;
}

.filter-row label {
  font-size: 0.86rem;
  color: var(--muted);
}

.filter-select {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.3rem 0.5rem;
  background: #fff;
  color: var(--text);
  font-size: 0.86rem;
}

.study-grid,
.cards-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.8rem;
}

.qa-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.7rem;
}

.qa-item {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.75rem;
  background: #fff;
}

.qa-q,
.qa-a {
  margin: 0;
}

.qa-q {
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.point-line {
  margin: 0 0 0.3rem;
  font-weight: 700;
  line-height: 1.45;
}

.points-plus-details summary {
  cursor: pointer;
  font-weight: 700;
  margin-bottom: 0.6rem;
}

.points-plus-details[open] summary {
  margin-bottom: 0.75rem;
}

.plus-list {
  margin-top: 0.2rem;
}

.status-correct {
  border-color: #16a34a !important;
  background: #f0fdf4 !important;
}

.status-wrong {
  border-color: #dc2626 !important;
  background: #fef2f2 !important;
}

.status-none {
  border-color: #cbd5e1 !important;
  background: #f8fafc !important;
}

.status-chip {
  display: inline-block;
  border: 2px solid var(--line);
  border-radius: 10px;
  padding: 0.1rem 0.55rem;
  font-size: 0.9rem;
  font-weight: 700;
  line-height: 1.4;
}

.quiz-table {
  width: 100%;
  border-collapse: collapse;
}

.quiz-table thead th {
  text-align: left;
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 600;
  padding: 0 0.5rem 0.25rem;
}

.quiz-table thead {
  display: none;
}

.quiz-table tbody {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.45rem;
}

.quiz-row {
  display: block;
}

.quiz-cell {
  border: 2px solid var(--line);
  border-radius: 10px;
  padding: 0;
  font-weight: 600;
  background: #fff;
}

.quiz-link {
  display: block;
  text-align: center;
  text-decoration: none;
  color: var(--text);
  padding: 0.55rem 0.4rem;
}

.quiz-row.status-correct .quiz-cell {
  border-color: #16a34a;
  background: #f0fdf4;
}

.quiz-row.status-wrong .quiz-cell {
  border-color: #dc2626;
  background: #fef2f2;
}

.quiz-row.status-none .quiz-cell {
  border-color: #cbd5e1;
  background: #f8fafc;
}

.error-panel {
  border: 1px solid #fecaca;
  background: #fff7f7;
  border-radius: 10px;
  padding: 0.75rem;
}

.fallback-links {
  display: flex;
  gap: 0.65rem;
  margin-top: 0.55rem;
  flex-wrap: wrap;
}

.btn {
  appearance: none;
  width: 100%;
  display: inline-block;
  text-align: center;
  text-decoration: none;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--text);
  border-radius: 10px;
  padding: 0.62rem 0.78rem;
  font-weight: 600;
  cursor: pointer;
}

.btn.primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.btn.primary:hover {
  background: var(--primary-strong);
}

.btn.secondary {
  background: #e8efff;
  border-color: #bfd3ff;
  color: #1e3a8a;
}

.btn.secondary:hover {
  background: #dbe7ff;
}

.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

.cta-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.45rem;
  margin-top: 0.62rem;
}

.choice-list {
  display: grid;
  gap: 0.45rem;
  margin-bottom: 0.42rem;
}

.quiz-nav {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.45rem;
}

.quiz-nav .btn {
  width: 100%;
}

.choice-btn {
  text-align: left;
}

.choice-btn.correct {
  border-color: #15803d;
  background: #f0fdf4;
}

.choice-btn.wrong {
  border-color: #dc2626;
  background: #fef2f2;
}

.result {
  min-height: 2.5rem;
  padding: 0.4rem 0;
}

.muted {
  color: var(--muted);
}

.center {
  text-align: center;
}

.site-footer {
  margin-top: 0.75rem;
  border-top: 1px solid var(--line);
  background: #fff;
}

.footer-inner {
  padding: 0.8rem 0 1rem;
}

.footer-links {
  display: flex;
  gap: 0.7rem;
  flex-wrap: wrap;
  margin-bottom: 0.35rem;
}

.footer-note {
  margin-bottom: 0.2rem;
  font-size: 0.82rem;
  color: var(--muted);
}

.footer-copy {
  margin: 0;
  font-size: 0.8rem;
  color: var(--muted);
}

@media (max-width: 430px) {
  body {
    font-size: 14px;
    line-height: 1.5;
  }

  h1 {
    font-size: 1.16rem;
  }

  h2 {
    font-size: 1rem;
  }

  .container {
    width: min(100% - 0.9rem, 760px);
  }

  .site-header {
    margin-bottom: 0.55rem;
  }

  .nav-wrap {
    padding: 0.48rem 0;
  }

  .nav-list {
    gap: 0.3rem;
  }

  .nav-list a {
    padding: 0.36rem 0.55rem;
    min-height: 2rem;
    font-size: 0.82rem;
  }

  .card,
  .hero {
    padding: 0.68rem;
    margin-bottom: 0.5rem;
  }

  .filter-row {
    gap: 0.3rem;
  }

  .filter-select {
    padding: 0.24rem 0.42rem;
    font-size: 0.82rem;
  }

  .btn {
    padding: 0.52rem 0.62rem;
    font-size: 0.92rem;
  }

  .cta-row,
  .choice-list,
  .quiz-nav {
    gap: 0.36rem;
  }

  .quiz-table tbody {
    gap: 0.34rem;
  }

  .quiz-link {
    padding: 0.44rem 0.3rem;
    font-size: 0.86rem;
  }

  .footer-note,
  .footer-copy {
    font-size: 0.76rem;
  }
}

@media (min-width: 700px) {
  h1 {
    font-size: 1.55rem;
  }

  .study-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .cards-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .cta-row {
    grid-template-columns: repeat(2, minmax(0, 260px));
  }

  .btn {
    width: auto;
  }

  .quiz-table tbody {
    grid-template-columns: repeat(6, minmax(0, 1fr));
  }
}