/* ============================================
   BUTTONS
   ============================================ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--radius-full);
  border: none;
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn-primary {
  background: var(--color-primary);
  color: white;
  padding: var(--spacing-md) var(--spacing-xl);
  font-family: var(--font-display);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-radius: 16px;
  box-shadow: 0 4px 0 0 var(--color-primary-hover), 0 6px 16px rgba(107,156,196,0.25);
  transition: all 0.1s;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 0 0 var(--color-primary-hover), 0 10px 24px rgba(107,156,196,0.3);
}

.btn-primary:active {
  transform: translateY(2px);
  box-shadow: 0 1px 0 0 var(--color-primary-hover), 0 2px 8px rgba(107,156,196,0.2);
}

.btn-secondary {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.btn-secondary:hover {
  background: #DDD6FE;
}

.btn-ghost {
  color: var(--color-text-muted);
  padding: var(--spacing-sm) var(--spacing-md);
}

.btn-ghost:hover {
  color: var(--color-text);
  background: var(--color-border-light);
}

/* ============================================
   TOPICS PAGE VIDEO HEADER
   ============================================ */

.topics-video-wrap {
  text-align: center;
  margin-bottom: var(--spacing-lg);
}

.topics-video {
  width: 100%;
  max-width: 100%;
  border-radius: 20px;
  box-shadow: 0 8px 32px rgba(107,156,196,0.15);
}

/* ============================================
   TOPIC CARDS
   ============================================ */

.topic-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
}

@media (min-width: 480px) {
  .topic-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 768px) {
  .topic-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.topic-card {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-card);
  cursor: pointer;
  transition: all 0.2s ease;
  border-left: 4px solid var(--color-primary);
}

.topic-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 6px 20px rgba(0,0,0,0.08);
}

.topic-card-icon {
  margin-bottom: var(--spacing-sm);
  line-height: 0;
}

.topic-card-icon svg {
  width: 48px;
  height: 48px;
}

.topic-card-title {
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
}

.topic-card-description {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  line-height: 1.5;
}

.topic-card-count {
  margin-top: var(--spacing-sm);
  font-size: 0.75rem;
  color: var(--color-text-light);
}

/* ============================================
   TUTORIAL LIST
   ============================================ */

.tutorial-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.tutorial-list-item {
  background: var(--color-surface);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  transition: all 0.2s ease;
}

.tutorial-list-item:hover {
  box-shadow: var(--shadow-card);
  transform: translateX(4px);
}

.tutorial-list-header {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-sm);
}

.tutorial-list-title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1rem;
}

.badge {
  display: inline-block;
  padding: 2px var(--spacing-sm);
  border-radius: var(--radius-full);
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.badge-warmup {
  background: var(--color-success-light);
  color: var(--color-success);
}

.badge-core {
  background: var(--color-accent-light);
  color: var(--color-accent);
}

.badge-challenge {
  background: var(--color-primary-light);
  color: var(--color-primary);
}

.tutorial-list-meta {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.material-chips {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-top: var(--spacing-sm);
}

.material-chip {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px var(--spacing-sm);
  background: var(--color-border-light);
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

/* ============================================
   SECTION HEADERS
   ============================================ */

/* ============================================
   CODI MASCOT PROMPT
   ============================================ */

.codi-prompt {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
}

.codi-img {
  width: 64px;
  height: 64px;
  border-radius: 16px;
  object-fit: cover;
  flex-shrink: 0;
  box-shadow: 0 4px 16px rgba(160, 152, 196, 0.2);
  animation: codiBounce 3s ease-in-out infinite;
}

@keyframes codiBounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-4px); }
}

.codi-speech {
  background: var(--color-surface);
  border-radius: 16px;
  padding: var(--spacing-md) var(--spacing-lg);
  box-shadow: 0 2px 12px rgba(107, 156, 196, 0.08);
  position: relative;
}

.codi-speech::before {
  content: '';
  position: absolute;
  left: -8px;
  top: 50%;
  transform: translateY(-50%);
  width: 0;
  height: 0;
  border-top: 8px solid transparent;
  border-bottom: 8px solid transparent;
  border-right: 8px solid var(--color-surface);
}

.codi-speech .section-title {
  margin-bottom: 2px;
}

.codi-speech .section-subtitle {
  margin-bottom: 0;
}

/* ============================================
   SECTION HEADERS
   ============================================ */

.section-header {
  margin-bottom: var(--spacing-xl);
}

.section-title {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: var(--spacing-xs);
}

.section-subtitle {
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  color: var(--color-text-muted);
  font-size: 0.85rem;
  margin-bottom: var(--spacing-md);
  cursor: pointer;
}

.back-link:hover {
  color: var(--color-primary);
}

/* ============================================
   DIAGRAMS
   ============================================ */

/* ============================================
   DIAGRAM: COLLAGE / CRAFT STYLE
   ============================================ */

.diagram-container {
  margin: var(--spacing-md) 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  background: linear-gradient(135deg, var(--color-bg) 0%, var(--color-bg-warm) 100%);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg) var(--spacing-md);
  position: relative;
}

.diagram-array {
  display: flex;
  gap: 6px;
}

.diagram-cell {
  width: 52px;
  height: 52px;
  border: 2px solid #bbb;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-hand);
  font-weight: 700;
  font-size: 1.4rem;
  color: var(--color-text);
  background: var(--color-surface);
  border-radius: 4px;
  box-shadow: var(--shadow-paper);
  transform: rotate(-0.5deg);
  position: relative;
  /* Lined paper effect */
  background-image: repeating-linear-gradient(
    transparent,
    transparent 11px,
    #d0dae8 11px,
    #d0dae8 12px
  );
  background-size: 100% 12px;
  background-position: 0 8px;
}

.diagram-cell:nth-child(odd) {
  transform: rotate(0.5deg);
}

.diagram-cell:nth-child(3n) {
  background-color: var(--color-blue-light);
}

.diagram-cell:nth-child(3n+1) {
  background-color: var(--color-surface);
}

.diagram-cell:nth-child(3n+2) {
  background-color: var(--color-pink-light);
}

.diagram-cell.empty {
  color: var(--color-text-light);
  background-color: var(--color-border-light);
  background-image: none;
  border-style: dashed;
  border-color: #ccc;
  box-shadow: none;
}

.diagram-cell.highlight {
  background-color: var(--color-yellow-light);
  border-color: var(--color-yellow);
  border-width: 2.5px;
  box-shadow: 0 0 0 3px rgba(244, 197, 84, 0.2), var(--shadow-paper);
}

.diagram-cell.swap-left,
.diagram-cell.swap-right {
  background-color: var(--color-accent-light);
  border-color: var(--color-accent);
}

.diagram-indices {
  display: flex;
  gap: 6px;
}

.diagram-index {
  width: 52px;
  text-align: center;
  font-family: var(--font-hand);
  font-size: 0.85rem;
  color: var(--color-text-muted);
  padding-top: 6px;
}

.diagram-pointer {
  position: relative;
  display: flex;
  gap: 6px;
}

.diagram-pointer-arrow {
  width: 52px;
  text-align: center;
  font-family: var(--font-hand);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--color-primary);
  padding-top: 6px;
}

.diagram-pointer-arrow::before {
  content: "\25B2";
  display: block;
  font-size: 0.65rem;
  color: var(--color-primary);
}

/* Call stack diagram */
.diagram-callstack {
  display: flex;
  flex-direction: column;
  gap: 6px;
  width: 100%;
  max-width: 340px;
}

.diagram-frame {
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: 6px;
  font-family: var(--font-hand);
  font-size: 1.05rem;
  font-weight: 700;
  text-align: center;
  border: 2px solid #bbb;
  background: var(--color-surface);
  box-shadow: var(--shadow-paper);
  transform: rotate(-0.8deg);
  position: relative;
  /* Paper texture */
  background-image: repeating-linear-gradient(
    transparent,
    transparent 11px,
    #d0dae8 11px,
    #d0dae8 12px
  );
  background-size: 100% 12px;
  background-position: 0 6px;
}

.diagram-frame:nth-child(even) {
  transform: rotate(0.6deg);
}

.diagram-frame:nth-child(1) { background-color: var(--color-blue-light); }
.diagram-frame:nth-child(2) { background-color: var(--color-pink-light); }
.diagram-frame:nth-child(3) { background-color: #F0ECD6; }
.diagram-frame:nth-child(4) { background-color: #D6F0D6; }

.diagram-frame.base-case {
  border: 2.5px solid var(--color-success);
  background-color: var(--color-success-light);
  box-shadow: 0 0 0 3px rgba(125, 184, 125, 0.15), var(--shadow-paper);
}

.diagram-frame.resolved {
  border: 2px solid var(--color-primary);
  background-color: var(--color-primary-light);
}

.diagram-frame .status {
  font-family: var(--font-hand);
  font-size: 0.85rem;
  font-weight: 400;
  color: var(--color-text-muted);
  display: block;
  margin-top: 2px;
}

/* Swap arrow */
.diagram-swap-row {
  display: flex;
  justify-content: center;
  padding: var(--spacing-xs) 0;
  font-family: var(--font-hand);
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--color-primary);
}

/* MidStack diagram */
.midstack-layout {
  display: flex;
  align-items: center;
  gap: 0;
  justify-content: center;
  flex-wrap: wrap;
}

.midstack-half {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-xs);
}

.midstack-label {
  font-family: var(--font-hand);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text-muted);
}

.midstack-divider {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0 var(--spacing-sm);
}

.midstack-divider-line {
  width: 2px;
  height: 48px;
  background: var(--color-accent);
  border-radius: 1px;
}

.midstack-divider-label {
  font-family: var(--font-hand);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--color-primary);
  margin-top: var(--spacing-xs);
}

.midstack-empty {
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 60px;
  height: 52px;
  border: 2px dashed #ccc;
  border-radius: 4px;
  color: var(--color-text-light);
  font-family: var(--font-hand);
  font-size: 1rem;
}

.midstack-note {
  text-align: center;
  font-family: var(--font-hand);
  font-size: 1rem;
  color: var(--color-text-muted);
  margin-top: var(--spacing-sm);
}