/* ============================================
   Chemistry Distilled — Lessons Styles
   ============================================ */

/* ---- Lessons Listing Page ---- */
.lessons-hero {
  background: linear-gradient(145deg, #1a2e1a 0%, #2a3f28 30%, #1e3028 60%, #162418 100%);
  padding: 140px 0 80px;
  text-align: center;
}

.lessons-hero .section-label {
  color: var(--terra-light);
}

.lessons-hero .section-title {
  color: #fff;
  margin-bottom: 12px;
}

.lessons-hero .section-intro {
  color: rgba(255, 255, 255, 0.75);
  margin: 0 auto;
}

.lessons-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
  padding: var(--section-pad) 0;
}

.lesson-card {
  background: var(--cream);
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid rgba(44, 36, 24, 0.06);
  transition: all 0.3s var(--ease);
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
}

.lesson-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 48px rgba(44, 36, 24, 0.1);
  color: inherit;
}

.lesson-card-thumb {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  background: var(--stone);
}

.lesson-card-thumb-placeholder {
  width: 100%;
  aspect-ratio: 16 / 9;
  background: linear-gradient(135deg, var(--sage) 0%, var(--sage-dark) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
  color: rgba(255, 255, 255, 0.4);
}

.lesson-card-body {
  padding: 20px 24px 24px;
  flex: 1;
  display: flex;
  flex-direction: column;
}

.lesson-card-meta {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
}

.lesson-tag {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  padding: 3px 10px;
  border-radius: 20px;
}

.lesson-tag-gcse {
  background: rgba(91, 117, 83, 0.12);
  color: var(--sage);
}

.lesson-tag-alevel {
  background: rgba(184, 107, 66, 0.12);
  color: var(--terracotta);
}

.lesson-tag-duration {
  background: var(--stone);
  color: var(--walnut);
}

.lesson-card-body h3 {
  font-family: var(--font-serif);
  font-size: 1.15rem;
  color: var(--bark);
  margin-bottom: 8px;
  line-height: 1.3;
}

.lesson-card-body p {
  font-size: 0.88rem;
  color: var(--walnut);
  line-height: 1.6;
  flex: 1;
}

.lesson-card-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--sage);
  margin-top: 16px;
  transition: gap 0.3s var(--ease);
}

.lesson-card:hover .lesson-card-link {
  gap: 10px;
  color: var(--terracotta);
}

/* ---- Individual Lesson Page ---- */
.lesson-banner {
  background: linear-gradient(145deg, #1a2e1a 0%, #2a3f28 30%, #1e3028 60%, #162418 100%);
  padding: 120px 0 48px;
}

.lesson-banner .section-label {
  color: var(--terra-light);
}

.lesson-banner-title {
  font-family: var(--font-serif);
  font-size: 2.6rem;
  font-weight: 600;
  color: #fff;
  line-height: 1.2;
  margin-bottom: 16px;
}

.lesson-banner-meta {
  display: flex;
  gap: 12px;
  align-items: center;
}

.lesson-layout {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 48px;
  padding: 48px 0 var(--section-pad);
  align-items: start;
}

/* Main content column */
.lesson-content {
  min-width: 0;
}

.lesson-content h2 {
  font-family: var(--font-serif);
  font-size: 1.6rem;
  color: var(--bark);
  margin: 40px 0 16px;
  padding-top: 8px;
}

.lesson-content h2:first-child {
  margin-top: 0;
}

.lesson-content h3 {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  color: var(--bark);
  margin: 28px 0 12px;
}

.lesson-content p {
  font-size: 1.02rem;
  color: var(--walnut);
  margin-bottom: 16px;
  line-height: 1.8;
}

.lesson-content ul,
.lesson-content ol {
  margin: 0 0 16px 24px;
  color: var(--walnut);
}

.lesson-content li {
  margin-bottom: 6px;
  line-height: 1.7;
}

.lesson-content strong {
  color: var(--bark);
}

.lesson-content img {
  border-radius: 8px;
  margin: 24px 0;
  box-shadow: 0 4px 16px rgba(44, 36, 24, 0.08);
}

/* Key concept callout */
.key-concept {
  background: rgba(91, 117, 83, 0.08);
  border-left: 4px solid var(--sage);
  border-radius: 0 8px 8px 0;
  padding: 20px 24px;
  margin: 24px 0;
}

.key-concept > strong:first-child {
  display: block;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--sage);
  margin-bottom: 8px;
}

.key-concept p {
  margin-bottom: 0;
}

/* Lesson diagrams/images */
.lesson-diagram {
  width: 100%;
  max-width: 720px;
  height: auto;
  border-radius: 8px;
  margin: 24px 0;
  box-shadow: 0 4px 16px rgba(44, 36, 24, 0.08);
  border: 1px solid rgba(44, 36, 24, 0.06);
}

/* Tables in lessons */
.lesson-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0 28px;
  font-size: 0.92rem;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--sand);
}

.lesson-content thead {
  background: var(--stone);
}

.lesson-content th {
  font-weight: 600;
  color: var(--bark);
  text-align: left;
  padding: 12px 16px;
  border-bottom: 2px solid var(--sand);
}

.lesson-content td {
  padding: 10px 16px;
  color: var(--walnut);
  border-bottom: 1px solid rgba(216, 208, 196, 0.5);
}

.lesson-content tbody tr:last-child td {
  border-bottom: none;
}

.lesson-content tbody tr:hover {
  background: rgba(237, 232, 224, 0.4);
}

/* Video embed */
.video-container {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 */
  height: 0;
  overflow: hidden;
  border-radius: 12px;
  margin: 32px 0;
  background: var(--bark);
  box-shadow: 0 8px 32px rgba(44, 36, 24, 0.12);
}

.video-container:has(video) {
  padding-bottom: 0;
  height: auto;
}

.video-container iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.video-container video {
  display: block;
  width: 100%;
  height: auto;
  border: none;
}

.video-placeholder {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: rgba(255, 255, 255, 0.5);
  font-size: 0.9rem;
  gap: 12px;
}

.video-placeholder span:first-child {
  font-size: 3rem;
}

/* Sidebar */
.lesson-sidebar {
  position: sticky;
  top: 100px;
}

.sidebar-toc {
  background: var(--stone);
  border-radius: 12px;
  padding: 24px;
  margin-bottom: 24px;
}

.sidebar-toc h4 {
  font-family: var(--font-serif);
  font-size: 1rem;
  color: var(--bark);
  margin-bottom: 16px;
}

.sidebar-toc ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sidebar-toc a {
  font-size: 0.88rem;
  color: var(--walnut);
  display: block;
  padding: 4px 0;
  border-left: 2px solid transparent;
  padding-left: 12px;
  transition: all 0.2s var(--ease);
}

.sidebar-toc a:hover {
  color: var(--sage);
  border-left-color: var(--sage);
}

.sidebar-cta {
  background: linear-gradient(160deg, #2a3f28 0%, #1e3028 50%, #1a2818 100%);
  border-radius: 12px;
  padding: 28px 24px;
  text-align: center;
  color: #fff;
  margin-bottom: 24px;
}

.sidebar-cta h4 {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  color: var(--gold-light);
  margin-bottom: 8px;
}

.sidebar-cta p {
  font-size: 0.88rem;
  color: rgba(255, 255, 255, 0.7);
  margin-bottom: 16px;
  line-height: 1.6;
}

.sidebar-cta .btn-primary {
  background: var(--terracotta);
  width: 100%;
}

.sidebar-cta .btn-primary:hover {
  background: var(--terra-light);
}

/* Prev/Next navigation */
.lesson-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  padding: 32px 0;
  border-top: 1px solid var(--sand);
  margin-top: 48px;
}

.lesson-nav-link {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px;
  background: var(--stone);
  border-radius: 8px;
  text-decoration: none;
  transition: all 0.3s var(--ease);
}

.lesson-nav-link:hover {
  background: var(--sand);
}

.lesson-nav-link.next {
  text-align: right;
}

.lesson-nav-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--terracotta);
}

.lesson-nav-title {
  font-family: var(--font-serif);
  font-size: 0.95rem;
  color: var(--bark);
}

/* ---- Element Symbol Card (inline HTML) ---- */
.element-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 140px;
  aspect-ratio: 5 / 6;
  border: 3px solid var(--sage);
  border-radius: 8px;
  background: var(--parchment);
  margin: 24px 0;
  padding: 12px 8px 10px;
  box-shadow: 0 4px 16px rgba(44, 36, 24, 0.08);
}

.element-card .element-mass {
  font-family: var(--font-sans);
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--walnut);
  line-height: 1;
}

.element-card .element-symbol {
  font-family: var(--font-serif);
  font-size: 3.2rem;
  font-weight: 600;
  color: var(--bark);
  line-height: 1.1;
}

.element-card .element-number {
  font-family: var(--font-sans);
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--walnut);
  line-height: 1;
}

.element-card .element-name {
  font-family: var(--font-sans);
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--terracotta);
  line-height: 1;
  margin-top: 2px;
}

/* ---- Responsive ---- */
@media (max-width: 1024px) {
  .lessons-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .lesson-layout {
    grid-template-columns: 1fr;
  }

  .lesson-sidebar {
    position: static;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
  }
}

@media (max-width: 768px) {
  .lessons-hero {
    padding: 120px 0 48px;
  }

  .lessons-grid {
    grid-template-columns: 1fr;
    max-width: 480px;
    margin: 0 auto;
  }

  .lesson-banner-title {
    font-size: 2rem;
  }

  .lesson-sidebar {
    grid-template-columns: 1fr;
  }

  .lesson-nav {
    grid-template-columns: 1fr;
  }
}