:root {
  --ink: #17212b;
  --paper: #fbf7ef;
  --chalk: #11202a;
  --teal: #2a7b9b;
  --vermillion: #d94f30;
  --forest: #2d8b55;
  --amber: #d4a843;
  --plum: #6c5c93;
}

body {
  background:
    linear-gradient(90deg, rgba(42, 123, 155, 0.05) 1px, transparent 1px),
    linear-gradient(0deg, rgba(42, 123, 155, 0.05) 1px, transparent 1px),
    var(--paper);
  background-size: 32px 32px;
}

.nav {
  border-bottom: 1px solid rgba(23, 33, 43, 0.08);
  backdrop-filter: blur(18px);
}

.nav-title {
  letter-spacing: 0;
}

.module {
  position: relative;
}

.module-content {
  max-width: 1080px;
}

.module-header {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(280px, 0.8fr);
  gap: var(--space-8);
  align-items: center;
}

.module-kicker {
  color: var(--teal);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.module-title {
  color: var(--ink);
  letter-spacing: 0;
}

.module-subtitle {
  max-width: 700px;
}

.hero-panel,
.proof-card,
.map-panel,
.source-strip,
.crossword-card,
.exam-console {
  background: rgba(255, 255, 255, 0.86);
  border: 1px solid rgba(23, 33, 43, 0.1);
  border-radius: 8px;
  box-shadow: 0 18px 45px rgba(23, 33, 43, 0.09);
}

.hero-panel {
  padding: var(--space-6);
  overflow: hidden;
}

.hero-panel img,
.slide-frame img {
  display: block;
  width: 100%;
  border-radius: 6px;
  border: 1px solid rgba(23, 33, 43, 0.08);
  background: #fff;
}

.proof-lab {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: var(--space-6);
  margin: var(--space-8) 0;
}

.proof-card {
  padding: var(--space-6);
}

.proof-card h3,
.map-panel h3,
.crossword-card h3,
.exam-console h3 {
  margin-top: 0;
}

.proof-state {
  background: var(--chalk);
  color: #d8f3ff;
  border-radius: 6px;
  padding: var(--space-5);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.7;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

.proof-state .goal {
  color: #f5d06f;
}

.proof-state .ctx {
  color: #92d6a5;
}

.rule-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-4);
  margin: var(--space-6) 0;
}

.rule-card {
  border-left: 4px solid var(--teal);
  background: rgba(255, 255, 255, 0.76);
  border-radius: 8px;
  padding: var(--space-5);
  box-shadow: var(--shadow-sm);
}

.rule-card:nth-child(2n) { border-left-color: var(--vermillion); }
.rule-card:nth-child(3n) { border-left-color: var(--forest); }
.rule-card:nth-child(4n) { border-left-color: var(--amber); }

.rule-card strong {
  display: block;
  margin-bottom: var(--space-2);
  font-family: var(--font-display);
  font-size: var(--text-lg);
}

.map-panel {
  padding: var(--space-6);
  margin: var(--space-8) 0;
}

.concept-map {
  display: grid;
  grid-template-columns: repeat(5, minmax(120px, 1fr));
  gap: var(--space-3);
  align-items: stretch;
}

.concept-node {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 76px;
  padding: var(--space-4);
  border-radius: 8px;
  background: #fff;
  border: 1px solid rgba(23, 33, 43, 0.1);
  text-align: center;
  font-weight: 700;
}

.concept-node.teal { box-shadow: inset 0 -4px 0 rgba(42, 123, 155, 0.35); }
.concept-node.red { box-shadow: inset 0 -4px 0 rgba(217, 79, 48, 0.35); }
.concept-node.green { box-shadow: inset 0 -4px 0 rgba(45, 139, 85, 0.35); }
.concept-node.amber { box-shadow: inset 0 -4px 0 rgba(212, 168, 67, 0.45); }
.concept-node.plum { box-shadow: inset 0 -4px 0 rgba(108, 92, 147, 0.35); }

.lecture-shot {
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: var(--space-6);
  align-items: center;
  margin: var(--space-8) 0;
}

.slide-frame {
  background: #fff;
  border: 1px solid rgba(23, 33, 43, 0.1);
  border-radius: 8px;
  padding: var(--space-4);
  box-shadow: var(--shadow-md);
}

.shoulder {
  border-top: 4px solid var(--plum);
  background: #fff;
  border-radius: 8px;
  padding: var(--space-6);
  margin: var(--space-8) 0;
}

.shoulder h3 {
  margin-top: 0;
}

.crossword-card {
  padding: var(--space-6);
  margin: var(--space-8) 0;
}

.real-crossword {
  display: grid;
  grid-template-columns: minmax(260px, 0.9fr) minmax(280px, 1.1fr);
  gap: var(--space-6);
  align-items: start;
}

.crossword-grid {
  display: grid;
  grid-template-columns: repeat(var(--cw-cols), minmax(0, 1fr));
  width: min(100%, 520px);
  aspect-ratio: var(--cw-cols) / var(--cw-rows);
  border: 2px solid var(--ink);
  background: var(--ink);
  gap: 2px;
  padding: 2px;
}

.cw-cell {
  position: relative;
  background: #fff;
  min-width: 0;
  min-height: 0;
}

.cw-cell.black {
  background: var(--ink);
}

.cw-cell input {
  width: 100%;
  height: 100%;
  border: 0;
  padding: 0;
  background: transparent;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(0.78rem, 2vw, 1.25rem);
  text-align: center;
  text-transform: uppercase;
  color: var(--ink);
}

.cw-cell input:focus {
  outline: 3px solid var(--color-accent-muted);
  outline-offset: -3px;
}

.cw-number {
  position: absolute;
  top: 2px;
  left: 3px;
  z-index: 1;
  font-family: var(--font-mono);
  font-size: clamp(0.45rem, 1vw, 0.65rem);
  font-weight: 800;
  color: var(--teal);
  pointer-events: none;
}

.crossword-clues {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-5);
}

.crossword-clues h4 {
  margin: 0 0 var(--space-3);
  color: var(--ink);
}

.crossword-clues ol {
  margin: 0;
  padding-left: var(--space-5);
  font-size: var(--text-sm);
  line-height: 1.55;
}

.crossword-clues li {
  margin-bottom: var(--space-2);
}

.answer-toggle {
  margin-top: var(--space-4);
  background: var(--color-accent-light);
  border-radius: 8px;
  padding: var(--space-4);
}

.crossword-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-top: var(--space-5);
}

.crossword-actions button {
  border: 1px solid rgba(23, 33, 43, 0.16);
  border-radius: 999px;
  background: #fff;
  padding: 0.55rem 0.9rem;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 800;
  cursor: pointer;
}

.crossword-actions button:first-child {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

.crossword-status {
  margin-top: var(--space-4);
  font-weight: 700;
  color: var(--color-text-secondary);
}

.cw-cell.correct input {
  background: rgba(45, 139, 85, 0.16);
}

.cw-cell.incorrect input {
  background: rgba(201, 59, 59, 0.16);
}

.source-strip {
  padding: var(--space-5);
  margin-top: var(--space-8);
  font-size: var(--text-sm);
  color: var(--color-text-secondary);
}

.exam-console {
  padding: var(--space-6);
  margin: var(--space-8) 0;
}

.exam-console ol {
  margin-bottom: 0;
}

.badge-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-5) 0;
}

.badge {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  border: 1px solid rgba(23, 33, 43, 0.12);
  background: #fff;
  padding: 0.35rem 0.7rem;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: 700;
}

.quiz-container {
  background: rgba(255,255,255,0.72);
}

.site-footer {
  display: flex;
  justify-content: center;
  position: relative;
  left: 50%;
  width: 100vw;
  max-width: none;
  margin: 5rem 0 2.5rem;
  padding: 2.35rem 1.25rem 2.65rem;
  border-top: 1px solid rgba(23, 33, 43, 0.12);
  background: transparent;
  box-shadow: none;
  text-align: center;
  transform: translateX(-50%);
}

.site-footer-line {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin: 0;
  color: var(--color-text-secondary);
  font-size: 1.65rem;
  font-weight: 600;
  line-height: 1.4;
  text-align: center;
}

.site-footer strong {
  color: var(--ink);
}

.site-footer-follow {
  margin-left: 0.2rem;
}

.site-footer-line .site-footer-icon-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 46px;
  width: 46px;
  height: 46px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  box-shadow: none;
  background: transparent;
  color: var(--color-accent);
  font-size: 0;
  line-height: 0;
  text-decoration: none !important;
  text-decoration-line: none !important;
  text-decoration-color: transparent !important;
  text-underline-offset: 0;
  vertical-align: middle;
}

.site-footer-line .site-footer-icon-link:visited,
.site-footer-line .site-footer-icon-link:active {
  border: 0;
  box-shadow: none;
  color: var(--color-accent);
  text-decoration: none !important;
  text-decoration-line: none !important;
}

.site-footer-line .site-footer-icon-link:hover,
.site-footer-line .site-footer-icon-link:focus-visible {
  background: var(--color-accent-light);
  border: 0;
  box-shadow: none;
  outline: none;
  text-decoration: none !important;
}

.site-footer-line svg {
  display: block;
  flex: 0 0 36px;
  width: 36px;
  height: 36px;
  min-width: 36px;
  max-width: 36px;
  min-height: 36px;
  max-height: 36px;
  overflow: hidden;
  fill: currentColor;
  stroke: currentColor;
  stroke-width: 1.8;
}

.site-footer-icon {
  inline-size: 36px !important;
  block-size: 36px !important;
}

.site-footer-line a:first-of-type svg {
  stroke-width: 0;
}

.site-footer-line a:last-of-type svg {
  fill: initial;
  stroke: none;
}

@media (max-width: 900px) {
  .module-header,
  .proof-lab,
  .lecture-shot {
    grid-template-columns: 1fr;
  }

  .rule-grid,
  .concept-map {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 600px) {
  .rule-grid,
  .concept-map,
  .real-crossword,
  .crossword-clues {
    grid-template-columns: 1fr;
  }

  .site-footer {
    margin: 3rem 0 1.5rem;
  }
}