/* Learn section — uses site palette from style.css */

:root {
  --chalk: var(--text-dim);
  --chalk-dim: var(--chrome-dim);
  --chalk-heading: var(--text);
  --chalk-highlight: var(--text);
  --chalk-link: var(--chrome);
  --board: var(--bg);
  --board-light: #333;
}

/* Lesson article */
.lesson {
  max-width: 720px;
  margin: 0 auto;
  padding: 3rem 1.5rem 2rem;
}

.lesson-unit {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--chalk-dim);
  margin-bottom: 0.3rem;
}

.lesson h1 {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 2rem;
  font-weight: 700;
  color: var(--chalk-heading);
  line-height: 1.2;
  margin-bottom: 0.6rem;
  letter-spacing: -0.01em;
}

.lesson .lesson-number {
  font-size: 0.85rem;
  color: var(--chalk-dim);
  margin-bottom: 2rem;
}

.lesson h2 {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.3rem;
  font-weight: 600;
  color: var(--chalk-heading);
  margin-top: 2.5rem;
  margin-bottom: 0.8rem;
}

.lesson h3 {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--chalk);
  margin-top: 1.8rem;
  margin-bottom: 0.5rem;
}

.lesson p {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.05rem;
  color: var(--chalk);
  line-height: 1.85;
  margin-bottom: 1.2rem;
}

.lesson ul, .lesson ol {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.05rem;
  color: var(--chalk);
  line-height: 1.85;
  margin: 0 0 1.2rem 1.5rem;
}

.lesson li {
  margin-bottom: 0.4rem;
}

.lesson strong {
  color: var(--chalk-heading);
  font-weight: 600;
}

.lesson em {
  color: var(--chalk-highlight);
  font-style: italic;
}

.lesson a {
  color: var(--chalk-link);
  border-bottom-color: var(--chrome-dim);
}

.lesson a:hover {
  color: #fff;
  border-bottom-color: #fff;
}

/* Chalkboard callout boxes */
.chalk-box {
  background: rgba(255, 255, 255, 0.04);
  border-left: 3px solid #555;
  padding: 1rem 1.2rem;
  margin: 1.5rem 0;
  border-radius: 0 6px 6px 0;
}

.chalk-box p {
  font-size: 0.95rem;
  margin-bottom: 0.5rem;
  color: var(--chalk-dim);
}

.chalk-box p:last-child {
  margin-bottom: 0;
}

.chalk-box strong {
  color: var(--chalk);
}

/* SVG diagram containers */
.diagram {
  margin: 2rem 0;
  text-align: center;
}

.diagram svg {
  max-width: 100%;
  height: auto;
}

.diagram-caption {
  font-size: 0.85rem;
  color: var(--chalk-dim);
  margin-top: 0.6rem;
  font-style: italic;
  font-family: Georgia, 'Times New Roman', serif;
}

/* Lesson navigation (prev/next) */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--board-light);
  gap: 1rem;
}

.lesson-nav a {
  font-size: 0.9rem;
  color: var(--chalk-link);
  border-bottom: none;
  padding: 0.5rem 0;
}

.lesson-nav a:hover {
  color: #fff;
}

.lesson-nav .prev::before {
  content: "\2190\00a0";
}

.lesson-nav .next::after {
  content: "\00a0\2192";
}

/* Sources section */
.lesson-sources {
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--board-light);
}

.lesson-sources h2 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--chalk-dim);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  margin-top: 0;
  margin-bottom: 0.8rem;
}

.lesson-sources ul {
  list-style: none;
  margin-left: 0;
  padding-left: 0;
  font-size: 0.85rem;
}

.lesson-sources li {
  margin-bottom: 0.3rem;
  color: var(--chalk-dim);
}

.lesson-sources a {
  color: var(--chalk-link);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  font-size: 0.85rem;
}

/* Syllabus page */
.syllabus {
  max-width: 720px;
  margin: 0 auto;
  padding: 3rem 1.5rem 2rem;
}

.syllabus h1 {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--chalk-heading);
  margin-bottom: 0.5rem;
  letter-spacing: -0.01em;
}

.syllabus .syllabus-intro {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.05rem;
  color: var(--chalk);
  line-height: 1.8;
  margin-bottom: 2.5rem;
}

.syllabus .unit {
  margin-bottom: 2rem;
}

.syllabus .unit-title {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--chrome);
  margin-bottom: 0.6rem;
  padding-bottom: 0.3rem;
  border-bottom: 1px solid var(--board-light);
  font-weight: 600;
}

.syllabus .lesson-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.syllabus .lesson-list li {
  margin-bottom: 0.4rem;
}

.syllabus .lesson-link {
  display: block;
  padding: 0.7rem 1rem;
  background: var(--surface);
  border: 1px solid #333;
  border-radius: 8px;
  border-bottom: 1px solid #333;
  transition: border-color 0.2s;
}

.syllabus .lesson-link:hover {
  border-color: var(--chrome);
}

.syllabus .lesson-link .num {
  font-size: 0.8rem;
  color: var(--chalk-dim);
  margin-right: 0.5rem;
  font-variant-numeric: tabular-nums;
}

.syllabus .lesson-link .title {
  font-size: 1rem;
  color: var(--chalk);
  font-weight: 500;
}

.syllabus .lesson-link .desc {
  display: block;
  font-size: 0.85rem;
  color: var(--chalk-dim);
  margin-top: 0.2rem;
  padding-left: 1.8rem;
  line-height: 1.5;
}

/* Responsive */
@media (max-width: 768px) {
  .lesson { padding: 2rem 1.5rem 1.5rem; }
  .lesson h1 { font-size: 1.7rem; }
  .syllabus { padding: 2rem 1.5rem 1.5rem; }
  .syllabus h1 { font-size: 1.8rem; }
}

@media (max-width: 540px) {
  .lesson { padding: 1.5rem 1rem 1.5rem; }
  .lesson h1 { font-size: 1.5rem; }
  .lesson h2 { font-size: 1.15rem; }
  .lesson p, .lesson ul, .lesson ol { font-size: 0.95rem; }
  .lesson-nav { flex-direction: column; align-items: flex-start; }
  .syllabus { padding: 1.5rem 1rem 1.5rem; }
  .syllabus h1 { font-size: 1.5rem; }
  .syllabus .lesson-link { padding: 0.6rem 0.8rem; }
  .syllabus .lesson-link .desc { padding-left: 0; }
}