/* ============================================================
   ZehnX Content Design System — zehnx-content.css
   Comprehensive CSS framework for all learning content.
   Dark theme, responsive, standalone — no framework dependency.
   ============================================================ */

/* --- Design Tokens --- */
:root {
  --zc-bg: #0a0a0f;
  --zc-card: #12121a;
  --zc-card2: #16161f;
  --zc-border: #1e1e2e;
  --zc-text: #e4e4e7;
  --zc-muted: #71717a;
  --zc-accent: #6366f1;
  --zc-gold: #d4a853;
  --zc-green: #34d399;
  --zc-red: #ef4444;
  --zc-orange: #f59e0b;
  --zc-blue: #3b82f6;
  --zc-purple: #8b5cf6;
  --zc-teal: #2dd4a8;
  --zc-font: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --zc-mono: "SF Mono", "Fira Code", "Consolas", monospace;
  --zc-radius: 12px;
  --zc-radius-sm: 8px;

  /* Spacing scale */
  --zc-space-xs: 4px;
  --zc-space-sm: 8px;
  --zc-space-md: 16px;
  --zc-space-lg: 24px;
  --zc-space-xl: 32px;
  --zc-space-2xl: 48px;

  /* Font sizes */
  --zc-fs-xs: 0.75rem;
  --zc-fs-sm: 0.875rem;
  --zc-fs-base: 1rem;
  --zc-fs-lg: 1.125rem;
  --zc-fs-xl: 1.25rem;
  --zc-fs-2xl: 1.5rem;
  --zc-fs-3xl: 1.875rem;
  --zc-fs-4xl: 2.25rem;

  /* Shadows */
  --zc-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --zc-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
  --zc-shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.5);
  --zc-shadow-glow: 0 0 20px rgba(99, 102, 241, 0.15);

  /* Transitions */
  --zc-transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --zc-transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --zc-transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);

  /* Glassmorphism */
  --zc-glass-bg: rgba(18, 18, 26, 0.7);
  --zc-glass-blur: 12px;
  --zc-glass-border: rgba(99, 102, 241, 0.12);
}


/* --- Reset & Base --- */
.zc-module *, .zc-module *::before, .zc-module *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* --- Accessibility: Focus States --- */
.zc-module *:focus-visible {
  outline: 2px solid var(--zc-accent);
  outline-offset: 2px;
  border-radius: 4px;
}

.zc-module button:focus-visible,
.zc-module a:focus-visible {
  outline: 2px solid var(--zc-accent);
  outline-offset: 2px;
  box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.2);
}

/* --- Reduced Motion --- */
@media (prefers-reduced-motion: reduce) {
  .zc-module *, .zc-module *::before, .zc-module *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* --- Skip-to-content for screen readers --- */
.zc-sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* ============================================================
   1. ZC-MODULE — Main Learning Module Wrapper
   ============================================================ */
.zc-module {
  font-family: var(--zc-font);
  color: var(--zc-text);
  background: var(--zc-bg);
  max-width: 860px;
  margin: 0 auto;
  padding: var(--zc-space-lg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Module Header */
.zc-module-header {
  margin-bottom: var(--zc-space-2xl);
  padding-bottom: var(--zc-space-lg);
  border-bottom: 1px solid var(--zc-border);
}

.zc-module-header__dept {
  display: inline-block;
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--zc-accent);
  margin-bottom: var(--zc-space-sm);
}

.zc-module-header__title {
  font-size: var(--zc-fs-3xl);
  font-weight: 700;
  color: #fff;
  line-height: 1.2;
  margin-bottom: var(--zc-space-sm);
}

.zc-module-header__subtitle {
  font-size: var(--zc-fs-lg);
  color: var(--zc-muted);
  margin-bottom: var(--zc-space-md);
}

.zc-module-header__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--zc-space-md);
  align-items: center;
}

.zc-module-header__meta-item {
  display: inline-flex;
  align-items: center;
  gap: var(--zc-space-xs);
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
}

.zc-module-header__meta-item svg {
  width: 16px;
  height: 16px;
  opacity: 0.7;
}

/* Difficulty Badges */
.zc-badge {
  display: inline-flex;
  align-items: center;
  padding: 2px 10px;
  border-radius: 999px;
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.zc-badge--beginner {
  background: rgba(52, 211, 153, 0.12);
  color: var(--zc-green);
  border: 1px solid rgba(52, 211, 153, 0.25);
}

.zc-badge--intermediate {
  background: rgba(245, 158, 11, 0.12);
  color: var(--zc-orange);
  border: 1px solid rgba(245, 158, 11, 0.25);
}

.zc-badge--advanced {
  background: rgba(239, 68, 68, 0.12);
  color: var(--zc-red);
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.zc-badge--expert {
  background: rgba(139, 92, 246, 0.12);
  color: var(--zc-purple);
  border: 1px solid rgba(139, 92, 246, 0.25);
}

/* Module Progress Indicator */
.zc-module-progress {
  display: flex;
  align-items: center;
  gap: var(--zc-space-sm);
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
  margin-top: var(--zc-space-md);
}

.zc-module-progress__bar {
  flex: 1;
  height: 4px;
  background: var(--zc-border);
  border-radius: 2px;
  overflow: hidden;
}

.zc-module-progress__fill {
  height: 100%;
  background: linear-gradient(90deg, var(--zc-accent), var(--zc-purple));
  border-radius: 2px;
  transition: width 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Module Footer / Sources */
.zc-module-footer {
  margin-top: var(--zc-space-2xl);
  padding-top: var(--zc-space-lg);
  border-top: 1px solid var(--zc-border);
}

.zc-module-footer__title {
  font-size: var(--zc-fs-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--zc-muted);
  margin-bottom: var(--zc-space-md);
}


/* ============================================================
   2. ZC-SECTION — Collapsible Section
   ============================================================ */
.zc-section {
  margin-bottom: var(--zc-space-xl);
}

.zc-section__header {
  display: flex;
  align-items: center;
  gap: var(--zc-space-sm);
  cursor: pointer;
  padding: var(--zc-space-md) 0;
  user-select: none;
  border-bottom: 1px solid transparent;
  transition: border-color var(--zc-transition);
}

.zc-section__header:hover {
  border-bottom-color: var(--zc-border);
}

.zc-section__chevron {
  width: 20px;
  height: 20px;
  color: var(--zc-muted);
  transition: transform var(--zc-transition);
  flex-shrink: 0;
}

.zc-section--collapsed .zc-section__chevron {
  transform: rotate(-90deg);
}

.zc-section__title {
  font-size: var(--zc-fs-xl);
  font-weight: 600;
  color: #fff;
}

.zc-section__body {
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.3s ease;
  opacity: 1;
}

.zc-section--collapsed .zc-section__body {
  max-height: 0 !important;
  opacity: 0;
}


/* ============================================================
   3. ZC-TEXT — Prose Text
   ============================================================ */
.zc-text {
  font-size: var(--zc-fs-base);
  line-height: 1.8;
  color: var(--zc-text);
  margin-bottom: var(--zc-space-lg);
}

.zc-text p {
  margin-bottom: 1em;
}

.zc-text p:last-child {
  margin-bottom: 0;
}

.zc-text strong {
  color: #fff;
  font-weight: 600;
}

.zc-text em {
  color: var(--zc-muted);
  font-style: italic;
}

.zc-text a {
  color: var(--zc-accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color var(--zc-transition-fast);
}

.zc-text a:hover {
  border-bottom-color: var(--zc-accent);
}

.zc-text code {
  font-family: var(--zc-mono);
  font-size: 0.9em;
  padding: 2px 6px;
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid rgba(99, 102, 241, 0.2);
  border-radius: 4px;
  color: var(--zc-accent);
}

.zc-text ul, .zc-text ol {
  padding-left: 1.5em;
  margin-bottom: 1em;
}

.zc-text li {
  margin-bottom: 0.4em;
}

.zc-text ul li::marker {
  color: var(--zc-accent);
}

.zc-text ol li::marker {
  color: var(--zc-accent);
  font-weight: 600;
}

.zc-text blockquote {
  border-left: 3px solid var(--zc-gold);
  padding: var(--zc-space-sm) var(--zc-space-md);
  margin: var(--zc-space-md) 0;
  background: rgba(212, 168, 83, 0.06);
  border-radius: 0 var(--zc-radius-sm) var(--zc-radius-sm) 0;
  color: var(--zc-muted);
  font-style: italic;
}


/* ============================================================
   4. ZC-HEADING — Section Headings
   ============================================================ */
.zc-heading {
  position: relative;
  padding-left: var(--zc-space-md);
  margin-bottom: var(--zc-space-lg);
  margin-top: var(--zc-space-2xl);
  color: #fff;
  font-weight: 700;
}

.zc-heading::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.15em;
  bottom: 0.15em;
  width: 3px;
  background: linear-gradient(180deg, var(--zc-accent), var(--zc-purple));
  border-radius: 2px;
}

.zc-heading--h2 {
  font-size: var(--zc-fs-2xl);
}

.zc-heading--h3 {
  font-size: var(--zc-fs-xl);
}

.zc-heading--h4 {
  font-size: var(--zc-fs-lg);
}


/* ============================================================
   5. ZC-INFOBOX — Colored Info Boxes
   ============================================================ */
.zc-infobox {
  position: relative;
  padding: var(--zc-space-md) var(--zc-space-lg);
  padding-left: calc(var(--zc-space-lg) + 36px);
  border-radius: var(--zc-radius);
  margin-bottom: var(--zc-space-lg);
  border: 1px solid;
  backdrop-filter: blur(var(--zc-glass-blur));
  -webkit-backdrop-filter: blur(var(--zc-glass-blur));
  transition: transform var(--zc-transition-fast), box-shadow var(--zc-transition-fast);
}

.zc-infobox:hover {
  transform: translateY(-1px);
  box-shadow: var(--zc-shadow);
}

.zc-infobox__icon {
  position: absolute;
  left: var(--zc-space-md);
  top: var(--zc-space-md);
  font-size: 1.2rem;
  line-height: 1;
}

.zc-infobox__title {
  font-weight: 600;
  margin-bottom: var(--zc-space-xs);
  font-size: var(--zc-fs-sm);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.zc-infobox__content {
  font-size: var(--zc-fs-sm);
  line-height: 1.7;
}

.zc-infobox__content p {
  margin-bottom: 0.5em;
}

.zc-infobox__content p:last-child {
  margin-bottom: 0;
}

/* Tip — green glassmorphism */
.zc-infobox--tip {
  background: linear-gradient(135deg, rgba(52, 211, 153, 0.08), rgba(52, 211, 153, 0.03));
  border-color: rgba(52, 211, 153, 0.2);
  box-shadow: inset 0 1px 0 rgba(52, 211, 153, 0.06);
}
.zc-infobox--tip .zc-infobox__title {
  color: var(--zc-green);
}

/* Warning — orange glassmorphism */
.zc-infobox--warning {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.08), rgba(245, 158, 11, 0.03));
  border-color: rgba(245, 158, 11, 0.2);
  box-shadow: inset 0 1px 0 rgba(245, 158, 11, 0.06);
}
.zc-infobox--warning .zc-infobox__title {
  color: var(--zc-orange);
}

/* Danger — red glassmorphism */
.zc-infobox--danger {
  background: linear-gradient(135deg, rgba(239, 68, 68, 0.08), rgba(239, 68, 68, 0.03));
  border-color: rgba(239, 68, 68, 0.2);
  box-shadow: inset 0 1px 0 rgba(239, 68, 68, 0.06);
}
.zc-infobox--danger .zc-infobox__title {
  color: var(--zc-red);
}

/* Info — blue glassmorphism */
.zc-infobox--info {
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.08), rgba(59, 130, 246, 0.03));
  border-color: rgba(59, 130, 246, 0.2);
  box-shadow: inset 0 1px 0 rgba(59, 130, 246, 0.06);
}
.zc-infobox--info .zc-infobox__title {
  color: var(--zc-blue);
}

/* Example — purple glassmorphism */
.zc-infobox--example {
  background: linear-gradient(135deg, rgba(139, 92, 246, 0.08), rgba(139, 92, 246, 0.03));
  border-color: rgba(139, 92, 246, 0.2);
  box-shadow: inset 0 1px 0 rgba(139, 92, 246, 0.06);
}
.zc-infobox--example .zc-infobox__title {
  color: var(--zc-purple);
}

/* Quote — gold glassmorphism */
.zc-infobox--quote {
  background: linear-gradient(135deg, rgba(212, 168, 83, 0.08), rgba(212, 168, 83, 0.03));
  border-color: rgba(212, 168, 83, 0.2);
  box-shadow: inset 0 1px 0 rgba(212, 168, 83, 0.06);
}
.zc-infobox--quote .zc-infobox__title {
  color: var(--zc-gold);
}


/* ============================================================
   6. ZC-CODE — Code Block
   ============================================================ */
.zc-code {
  position: relative;
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  margin-bottom: var(--zc-space-lg);
  overflow: hidden;
}

.zc-code__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--zc-space-sm) var(--zc-space-md);
  background: var(--zc-card2);
  border-bottom: 1px solid var(--zc-border);
}

.zc-code__lang {
  font-family: var(--zc-mono);
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.zc-code__copy {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 10px;
  background: transparent;
  border: 1px solid var(--zc-border);
  border-radius: 6px;
  color: var(--zc-muted);
  font-size: var(--zc-fs-xs);
  font-family: var(--zc-font);
  cursor: pointer;
  transition: all var(--zc-transition-fast);
}

.zc-code__copy:hover {
  border-color: var(--zc-accent);
  color: var(--zc-accent);
}

.zc-code__copy--copied {
  border-color: var(--zc-green);
  color: var(--zc-green);
}

.zc-code__body {
  padding: var(--zc-space-md);
  overflow-x: auto;
}

.zc-code__body pre {
  margin: 0;
  font-family: var(--zc-mono);
  font-size: var(--zc-fs-sm);
  line-height: 1.6;
  color: var(--zc-text);
  white-space: pre;
  tab-size: 2;
}

/* Typing cursor on code blocks when focused */
.zc-code:hover .zc-code__body pre::after {
  content: "\2588";
  color: var(--zc-accent);
  animation: zcBlink 1s step-end infinite;
  font-weight: 400;
}

@keyframes zcBlink {
  50% { opacity: 0; }
}

/* Syntax highlighting tokens */
.zc-code .tok-keyword { color: var(--zc-purple); }
.zc-code .tok-string { color: var(--zc-green); }
.zc-code .tok-number { color: var(--zc-orange); }
.zc-code .tok-comment { color: var(--zc-muted); font-style: italic; }
.zc-code .tok-function { color: var(--zc-blue); }
.zc-code .tok-operator { color: var(--zc-red); }
.zc-code .tok-variable { color: var(--zc-teal); }
.zc-code .tok-class { color: var(--zc-gold); }
.zc-code .tok-builtin { color: var(--zc-accent); }
.zc-code .tok-property { color: var(--zc-text); }
.zc-code .tok-punctuation { color: var(--zc-muted); }


/* ============================================================
   7. ZC-DIAGRAM — SVG Diagram Container
   ============================================================ */
.zc-diagram {
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  padding: var(--zc-space-lg);
  margin-bottom: var(--zc-space-lg);
  text-align: center;
  overflow: hidden;
}

.zc-diagram__title {
  font-size: var(--zc-fs-sm);
  font-weight: 600;
  color: var(--zc-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: var(--zc-space-md);
  text-align: left;
}

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

/* Diagram text styling */
.zc-diagram text {
  font-family: var(--zc-font);
  fill: var(--zc-text);
}

.zc-diagram .diagram-label {
  font-size: 12px;
  fill: var(--zc-muted);
}

.zc-diagram .diagram-value {
  font-size: 13px;
  font-weight: 600;
  fill: #fff;
}

/* Animated bars */
.zc-diagram--bar .bar-fill {
  transition: height 0.8s cubic-bezier(0.4, 0, 0.2, 1),
              y 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Radar chart */
.zc-diagram--radar .radar-area {
  transition: all 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Flow diagram */
.zc-diagram--flow .flow-node {
  transition: opacity 0.3s ease;
}

.zc-diagram--flow .flow-node:hover {
  opacity: 0.8;
}

/* Comparison */
.zc-diagram--comparison {
  display: flex;
  gap: var(--zc-space-md);
}

@media (max-width: 640px) {
  .zc-diagram--comparison {
    flex-direction: column;
  }
}


/* ============================================================
   8. ZC-TABS — Tab Interface
   ============================================================ */
.zc-tabs {
  margin-bottom: var(--zc-space-lg);
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  overflow: hidden;
}

.zc-tabs__header {
  display: flex;
  border-bottom: 1px solid var(--zc-border);
  overflow-x: auto;
  scrollbar-width: none;
}

.zc-tabs__header::-webkit-scrollbar {
  display: none;
}

.zc-tabs__tab {
  flex: 1;
  min-width: 0;
  padding: var(--zc-space-md) var(--zc-space-lg);
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--zc-muted);
  font-family: var(--zc-font);
  font-size: var(--zc-fs-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--zc-transition-fast);
  white-space: nowrap;
  text-align: center;
}

.zc-tabs__tab:hover {
  color: var(--zc-text);
  background: rgba(99, 102, 241, 0.04);
}

.zc-tabs__tab--active {
  color: var(--zc-accent);
  border-bottom-color: var(--zc-accent);
  background: rgba(99, 102, 241, 0.06);
}

.zc-tabs__panel {
  display: none;
  padding: var(--zc-space-lg);
  animation: zcFadeIn 0.25s ease;
}

.zc-tabs__panel--active {
  display: block;
}

@keyframes zcFadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to   { opacity: 1; transform: translateY(0); }
}


/* ============================================================
   9. ZC-ACCORDION — Collapsible Sections
   ============================================================ */
.zc-accordion {
  margin-bottom: var(--zc-space-lg);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  overflow: hidden;
}

.zc-accordion__item {
  border-bottom: 1px solid var(--zc-border);
}

.zc-accordion__item:last-child {
  border-bottom: none;
}

.zc-accordion__trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--zc-space-md) var(--zc-space-lg);
  background: var(--zc-card);
  border: none;
  color: var(--zc-text);
  font-family: var(--zc-font);
  font-size: var(--zc-fs-base);
  font-weight: 500;
  text-align: left;
  cursor: pointer;
  transition: background var(--zc-transition-fast);
}

.zc-accordion__trigger:hover {
  background: var(--zc-card2);
}

.zc-accordion__icon {
  width: 20px;
  height: 20px;
  color: var(--zc-muted);
  transition: transform var(--zc-transition);
  flex-shrink: 0;
}

.zc-accordion__item--open .zc-accordion__icon {
  transform: rotate(180deg);
}

.zc-accordion__content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(0.4, 0, 0.2, 1),
              padding 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  background: var(--zc-card2);
}

.zc-accordion__item--open .zc-accordion__content {
  max-height: 2000px;
}

.zc-accordion__content-inner {
  padding: 0 var(--zc-space-lg) var(--zc-space-lg);
  font-size: var(--zc-fs-sm);
  line-height: 1.7;
  color: var(--zc-muted);
}

.zc-accordion__item--open .zc-accordion__content-inner {
  padding-top: var(--zc-space-md);
}


/* ============================================================
   10. ZC-QUIZ — Quiz Component
   ============================================================ */
.zc-quiz {
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  padding: var(--zc-space-lg);
  margin-bottom: var(--zc-space-lg);
}

.zc-quiz__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--zc-space-md);
}

.zc-quiz__label {
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--zc-accent);
}

.zc-quiz-progress {
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
}

.zc-quiz-question {
  font-size: var(--zc-fs-lg);
  font-weight: 600;
  color: #fff;
  margin-bottom: var(--zc-space-lg);
  line-height: 1.5;
}

.zc-quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--zc-space-sm);
  margin-bottom: var(--zc-space-md);
}

.zc-quiz-option {
  display: flex;
  align-items: center;
  gap: var(--zc-space-md);
  padding: var(--zc-space-md) var(--zc-space-lg);
  background: var(--zc-card2);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius-sm);
  cursor: pointer;
  transition: all var(--zc-transition-fast);
  font-family: var(--zc-font);
  font-size: var(--zc-fs-base);
  color: var(--zc-text);
  text-align: left;
  width: 100%;
  position: relative;
  overflow: hidden;
}

/* Ripple effect on quiz options */
.zc-quiz-option::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0;
  height: 0;
  border-radius: 50%;
  background: rgba(99, 102, 241, 0.15);
  transform: translate(-50%, -50%);
  transition: width 0.5s ease, height 0.5s ease, opacity 0.5s ease;
  opacity: 0;
  pointer-events: none;
}

.zc-quiz-option:active:not(.zc-quiz-option--disabled)::after {
  width: 300px;
  height: 300px;
  opacity: 1;
  transition: width 0s, height 0s, opacity 0s;
}

.zc-quiz-option:hover:not(.zc-quiz-option--disabled) {
  border-color: var(--zc-accent);
  background: rgba(99, 102, 241, 0.06);
}

.zc-quiz-option__letter {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: rgba(99, 102, 241, 0.12);
  color: var(--zc-accent);
  font-size: var(--zc-fs-sm);
  font-weight: 700;
  flex-shrink: 0;
  transition: all var(--zc-transition-fast);
}

.zc-quiz-option--selected .zc-quiz-option__letter {
  background: var(--zc-accent);
  color: #fff;
}

.zc-quiz-option--correct {
  border-color: var(--zc-green) !important;
  background: rgba(52, 211, 153, 0.08) !important;
}

.zc-quiz-option--correct .zc-quiz-option__letter {
  background: var(--zc-green);
  color: #fff;
}

.zc-quiz-option--incorrect {
  border-color: var(--zc-red) !important;
  background: rgba(239, 68, 68, 0.08) !important;
}

.zc-quiz-option--incorrect .zc-quiz-option__letter {
  background: var(--zc-red);
  color: #fff;
}

.zc-quiz-option--disabled {
  cursor: default;
  opacity: 0.6;
}

.zc-quiz-option--disabled.zc-quiz-option--correct,
.zc-quiz-option--disabled.zc-quiz-option--incorrect {
  opacity: 1;
}

.zc-quiz-feedback {
  padding: var(--zc-space-md) var(--zc-space-lg);
  border-radius: var(--zc-radius-sm);
  font-size: var(--zc-fs-sm);
  line-height: 1.7;
  animation: zcFadeIn 0.3s ease;
}

.zc-quiz-feedback--correct {
  background: rgba(52, 211, 153, 0.08);
  border: 1px solid rgba(52, 211, 153, 0.2);
  color: var(--zc-green);
}

.zc-quiz-feedback--incorrect {
  background: rgba(239, 68, 68, 0.08);
  border: 1px solid rgba(239, 68, 68, 0.2);
  color: var(--zc-red);
}

.zc-quiz-feedback__title {
  font-weight: 600;
  margin-bottom: var(--zc-space-xs);
}

.zc-quiz-feedback__text {
  color: var(--zc-muted);
}


/* ============================================================
   11. ZC-EXERCISE — Interactive Exercise Block
   ============================================================ */
.zc-exercise {
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-left: 3px solid var(--zc-accent);
  border-radius: var(--zc-radius);
  padding: var(--zc-space-lg);
  margin-bottom: var(--zc-space-lg);
}

.zc-exercise__label {
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--zc-accent);
  margin-bottom: var(--zc-space-sm);
}

.zc-exercise__title {
  font-size: var(--zc-fs-xl);
  font-weight: 700;
  color: #fff;
  margin-bottom: var(--zc-space-sm);
}

.zc-exercise__desc {
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
  margin-bottom: var(--zc-space-lg);
  line-height: 1.7;
}

.zc-exercise__steps {
  list-style: none;
  padding: 0;
  margin-bottom: var(--zc-space-lg);
}

.zc-exercise__step {
  display: flex;
  align-items: flex-start;
  gap: var(--zc-space-md);
  padding: var(--zc-space-sm) 0;
  font-size: var(--zc-fs-sm);
  color: var(--zc-text);
}

.zc-exercise__step-check {
  width: 20px;
  height: 20px;
  border: 2px solid var(--zc-border);
  border-radius: 4px;
  cursor: pointer;
  flex-shrink: 0;
  margin-top: 1px;
  transition: all var(--zc-transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  padding: 0;
  color: transparent;
  font-size: 12px;
}

.zc-exercise__step-check:hover {
  border-color: var(--zc-accent);
}

.zc-exercise__step-check--done {
  background: var(--zc-accent);
  border-color: var(--zc-accent);
  color: #fff;
}

.zc-exercise__step--done {
  color: var(--zc-muted);
  text-decoration: line-through;
}

.zc-exercise__solution-toggle {
  display: inline-flex;
  align-items: center;
  gap: var(--zc-space-sm);
  padding: var(--zc-space-sm) var(--zc-space-md);
  background: transparent;
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius-sm);
  color: var(--zc-muted);
  font-family: var(--zc-font);
  font-size: var(--zc-fs-sm);
  cursor: pointer;
  transition: all var(--zc-transition-fast);
}

.zc-exercise__solution-toggle:hover {
  border-color: var(--zc-accent);
  color: var(--zc-accent);
}

.zc-exercise__solution {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

.zc-exercise__solution--open {
  max-height: 2000px;
}

.zc-exercise__solution-inner {
  padding-top: var(--zc-space-md);
  margin-top: var(--zc-space-md);
  border-top: 1px solid var(--zc-border);
  font-size: var(--zc-fs-sm);
  line-height: 1.7;
  color: var(--zc-muted);
}

/* Exercise completion indicator */
.zc-exercise__complete {
  display: flex;
  align-items: center;
  gap: var(--zc-space-sm);
  padding: var(--zc-space-sm) var(--zc-space-md);
  background: rgba(52, 211, 153, 0.08);
  border: 1px solid rgba(52, 211, 153, 0.2);
  border-radius: var(--zc-radius-sm);
  color: var(--zc-green);
  font-size: var(--zc-fs-sm);
  font-weight: 500;
  margin-top: var(--zc-space-md);
  animation: zcFadeIn 0.3s ease;
}


/* ============================================================
   12. ZC-KEYPOINT — Key Takeaway Card
   ============================================================ */
.zc-keypoint {
  display: flex;
  gap: var(--zc-space-md);
  padding: var(--zc-space-lg);
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.08), rgba(139, 92, 246, 0.06));
  border: 1px solid rgba(99, 102, 241, 0.2);
  border-radius: var(--zc-radius);
  margin-bottom: var(--zc-space-lg);
  backdrop-filter: blur(var(--zc-glass-blur));
  -webkit-backdrop-filter: blur(var(--zc-glass-blur));
  transition: transform var(--zc-transition-fast), box-shadow var(--zc-transition-fast);
  position: relative;
  overflow: hidden;
}

.zc-keypoint:hover {
  transform: translateY(-1px);
  box-shadow: var(--zc-shadow-glow);
}

.zc-keypoint::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 3px;
  background: linear-gradient(180deg, var(--zc-accent), var(--zc-purple));
  border-radius: 3px 0 0 3px;
}

.zc-keypoint__icon {
  font-size: 1.5rem;
  flex-shrink: 0;
  line-height: 1;
}

.zc-keypoint__content {
  font-size: var(--zc-fs-base);
  line-height: 1.7;
  color: var(--zc-text);
  font-weight: 500;
}

.zc-keypoint__content strong {
  color: #fff;
}


/* ============================================================
   13. ZC-TIMELINE — Vertical Timeline
   ============================================================ */
.zc-timeline {
  position: relative;
  padding-left: var(--zc-space-xl);
  margin-bottom: var(--zc-space-lg);
}

.zc-timeline::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 4px;
  bottom: 4px;
  width: 2px;
  background: var(--zc-border);
}

.zc-timeline__item {
  position: relative;
  padding-bottom: var(--zc-space-lg);
}

.zc-timeline__item:last-child {
  padding-bottom: 0;
}

.zc-timeline__dot {
  position: absolute;
  left: calc(-1 * var(--zc-space-xl) + 3px);
  top: 4px;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--zc-accent);
  border: 2px solid var(--zc-bg);
  box-shadow: 0 0 0 2px var(--zc-accent);
}

.zc-timeline__date {
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  color: var(--zc-accent);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: var(--zc-space-xs);
}

.zc-timeline__title {
  font-size: var(--zc-fs-base);
  font-weight: 600;
  color: #fff;
  margin-bottom: var(--zc-space-xs);
}

.zc-timeline__content {
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
  line-height: 1.7;
}


/* ============================================================
   14. ZC-COMPARISON — Two-Column Comparison
   ============================================================ */
.zc-comparison {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  overflow: hidden;
  margin-bottom: var(--zc-space-lg);
}

@media (max-width: 640px) {
  .zc-comparison {
    grid-template-columns: 1fr;
  }
}

.zc-comparison__col {
  padding: 0;
}

.zc-comparison__col:first-child {
  border-right: 1px solid var(--zc-border);
}

@media (max-width: 640px) {
  .zc-comparison__col:first-child {
    border-right: none;
    border-bottom: 1px solid var(--zc-border);
  }
}

.zc-comparison__header {
  padding: var(--zc-space-md) var(--zc-space-lg);
  font-weight: 600;
  font-size: var(--zc-fs-sm);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  border-bottom: 1px solid var(--zc-border);
}

.zc-comparison__col:first-child .zc-comparison__header {
  background: rgba(52, 211, 153, 0.06);
  color: var(--zc-green);
}

.zc-comparison__col:last-child .zc-comparison__header {
  background: rgba(239, 68, 68, 0.06);
  color: var(--zc-red);
}

.zc-comparison__items {
  list-style: none;
  padding: var(--zc-space-md) var(--zc-space-lg);
}

.zc-comparison__item {
  display: flex;
  align-items: flex-start;
  gap: var(--zc-space-sm);
  padding: var(--zc-space-sm) 0;
  font-size: var(--zc-fs-sm);
  color: var(--zc-text);
  line-height: 1.5;
}

.zc-comparison__item::before {
  content: "";
  width: 6px;
  height: 6px;
  border-radius: 50%;
  flex-shrink: 0;
  margin-top: 6px;
}

.zc-comparison__col:first-child .zc-comparison__item::before {
  background: var(--zc-green);
}

.zc-comparison__col:last-child .zc-comparison__item::before {
  background: var(--zc-red);
}


/* ============================================================
   15. ZC-PROGRESS — Lesson Progress Bar
   ============================================================ */
.zc-progress {
  margin-bottom: var(--zc-space-lg);
}

.zc-progress__label {
  display: flex;
  justify-content: space-between;
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
  margin-bottom: var(--zc-space-sm);
}

.zc-progress__bar {
  height: 6px;
  background: var(--zc-border);
  border-radius: 3px;
  overflow: hidden;
}

.zc-progress__fill {
  height: 100%;
  background: linear-gradient(90deg, var(--zc-accent), var(--zc-purple));
  border-radius: 3px;
  transition: width 0.8s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
}

.zc-progress__fill::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg,
    transparent 0%,
    rgba(255, 255, 255, 0.15) 50%,
    transparent 100%
  );
  animation: zcShimmer 2s infinite;
}

@keyframes zcShimmer {
  0%   { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}


/* ============================================================
   16. ZC-SOURCE — Source Citation
   ============================================================ */
.zc-source {
  display: flex;
  align-items: flex-start;
  gap: var(--zc-space-md);
  padding: var(--zc-space-md);
  background: var(--zc-card2);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius-sm);
  margin-bottom: var(--zc-space-sm);
  transition: border-color var(--zc-transition-fast);
}

.zc-source:hover {
  border-color: var(--zc-accent);
}

.zc-source__number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: rgba(99, 102, 241, 0.12);
  color: var(--zc-accent);
  font-size: var(--zc-fs-xs);
  font-weight: 700;
  flex-shrink: 0;
}

.zc-source__body {
  flex: 1;
  min-width: 0;
}

.zc-source__title {
  font-size: var(--zc-fs-sm);
  font-weight: 500;
  color: var(--zc-text);
  margin-bottom: 2px;
}

.zc-source__title a {
  color: inherit;
  text-decoration: none;
  transition: color var(--zc-transition-fast);
}

.zc-source__title a:hover {
  color: var(--zc-accent);
}

.zc-source__url {
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.zc-source__relevance {
  font-size: var(--zc-fs-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  flex-shrink: 0;
}

.zc-source__relevance--high {
  color: var(--zc-green);
}

.zc-source__relevance--medium {
  color: var(--zc-orange);
}

.zc-source__relevance--low {
  color: var(--zc-muted);
}


/* ============================================================
   17. ZC-NAV — Lesson Navigation
   ============================================================ */
.zc-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--zc-space-md);
  padding: var(--zc-space-lg) 0;
  margin-top: var(--zc-space-xl);
  border-top: 1px solid var(--zc-border);
}

.zc-nav__btn {
  display: inline-flex;
  align-items: center;
  gap: var(--zc-space-sm);
  padding: var(--zc-space-sm) var(--zc-space-lg);
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius-sm);
  color: var(--zc-text);
  font-family: var(--zc-font);
  font-size: var(--zc-fs-sm);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--zc-transition-fast);
  text-decoration: none;
}

.zc-nav__btn:hover {
  border-color: var(--zc-accent);
  color: var(--zc-accent);
}

.zc-nav__btn--disabled {
  opacity: 0.4;
  pointer-events: none;
}

.zc-nav__btn--primary {
  background: var(--zc-accent);
  border-color: var(--zc-accent);
  color: #fff;
}

.zc-nav__btn--primary:hover {
  background: #5558e6;
  border-color: #5558e6;
  color: #fff;
}

.zc-nav__overview {
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
  text-decoration: none;
  transition: color var(--zc-transition-fast);
}

.zc-nav__overview:hover {
  color: var(--zc-accent);
}


/* ============================================================
   18. ZC-MEDIA — Image/Video Placeholder
   ============================================================ */
.zc-media {
  margin-bottom: var(--zc-space-lg);
  border-radius: var(--zc-radius);
  overflow: hidden;
  border: 1px solid var(--zc-border);
}

.zc-media__content {
  position: relative;
  background: var(--zc-card);
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.zc-media__content img,
.zc-media__content video {
  display: block;
  width: 100%;
  height: auto;
}

.zc-media__placeholder {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--zc-space-sm);
  color: var(--zc-muted);
  font-size: var(--zc-fs-sm);
}

.zc-media__placeholder svg {
  width: 48px;
  height: 48px;
  opacity: 0.4;
}

.zc-media__caption {
  padding: var(--zc-space-sm) var(--zc-space-md);
  background: var(--zc-card2);
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
  text-align: center;
  border-top: 1px solid var(--zc-border);
}


/* ============================================================
   19. ZC-STAT — Statistic Highlight Card
   ============================================================ */
.zc-stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--zc-space-xl) var(--zc-space-lg);
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  margin-bottom: var(--zc-space-lg);
  text-align: center;
  position: relative;
  overflow: hidden;
  transition: transform var(--zc-transition-fast), box-shadow var(--zc-transition-fast);
}

.zc-stat:hover {
  transform: translateY(-2px);
  box-shadow: var(--zc-shadow-glow);
}

/* Subtle gradient accent line at top */
.zc-stat::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--zc-accent), var(--zc-purple), var(--zc-teal));
}

.zc-stat__value {
  font-size: var(--zc-fs-4xl);
  font-weight: 800;
  background: linear-gradient(135deg, var(--zc-accent), var(--zc-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
  margin-bottom: var(--zc-space-sm);
}

.zc-stat__label {
  font-size: var(--zc-fs-sm);
  color: var(--zc-muted);
  max-width: 280px;
}

/* Stat group — inline stats */
.zc-stat-group {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: var(--zc-space-md);
  margin-bottom: var(--zc-space-lg);
}

.zc-stat-group .zc-stat {
  margin-bottom: 0;
}


/* ============================================================
   20. ZC-CHECKLIST — Interactive Checklist
   ============================================================ */
.zc-checklist {
  background: var(--zc-card);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius);
  padding: var(--zc-space-lg);
  margin-bottom: var(--zc-space-lg);
}

.zc-checklist__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--zc-space-md);
}

.zc-checklist__title {
  font-size: var(--zc-fs-sm);
  font-weight: 600;
  color: var(--zc-text);
}

.zc-checklist__counter {
  font-size: var(--zc-fs-xs);
  color: var(--zc-muted);
}

.zc-checklist__progress {
  height: 3px;
  background: var(--zc-border);
  border-radius: 2px;
  margin-bottom: var(--zc-space-md);
  overflow: hidden;
}

.zc-checklist__progress-fill {
  height: 100%;
  background: var(--zc-green);
  border-radius: 2px;
  transition: width 0.4s ease;
}

.zc-checklist__items {
  list-style: none;
  padding: 0;
}

.zc-checklist__item {
  display: flex;
  align-items: center;
  gap: var(--zc-space-md);
  padding: var(--zc-space-sm) 0;
  border-bottom: 1px solid rgba(30, 30, 46, 0.5);
  cursor: pointer;
  transition: opacity var(--zc-transition-fast);
}

.zc-checklist__item:last-child {
  border-bottom: none;
}

.zc-checklist__checkbox {
  width: 20px;
  height: 20px;
  border: 2px solid var(--zc-border);
  border-radius: 4px;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--zc-transition-fast);
  background: transparent;
  padding: 0;
  cursor: pointer;
  color: transparent;
  font-size: 12px;
}

.zc-checklist__checkbox:hover {
  border-color: var(--zc-green);
}

.zc-checklist__item--checked .zc-checklist__checkbox {
  background: var(--zc-green);
  border-color: var(--zc-green);
  color: #fff;
}

.zc-checklist__item-text {
  font-size: var(--zc-fs-sm);
  color: var(--zc-text);
  transition: all var(--zc-transition-fast);
}

.zc-checklist__item--checked .zc-checklist__item-text {
  color: var(--zc-muted);
  text-decoration: line-through;
}


/* ============================================================
   UTILITY CLASSES
   ============================================================ */

/* Spacing */
.zc-mt-0 { margin-top: 0; }
.zc-mt-sm { margin-top: var(--zc-space-sm); }
.zc-mt-md { margin-top: var(--zc-space-md); }
.zc-mt-lg { margin-top: var(--zc-space-lg); }
.zc-mt-xl { margin-top: var(--zc-space-xl); }

.zc-mb-0 { margin-bottom: 0; }
.zc-mb-sm { margin-bottom: var(--zc-space-sm); }
.zc-mb-md { margin-bottom: var(--zc-space-md); }
.zc-mb-lg { margin-bottom: var(--zc-space-lg); }
.zc-mb-xl { margin-bottom: var(--zc-space-xl); }

/* Text */
.zc-text-center { text-align: center; }
.zc-text-muted { color: var(--zc-muted); }
.zc-text-accent { color: var(--zc-accent); }
.zc-text-sm { font-size: var(--zc-fs-sm); }
.zc-text-xs { font-size: var(--zc-fs-xs); }
.zc-text-bold { font-weight: 600; }

/* Display */
.zc-hidden { display: none; }
.zc-flex { display: flex; }
.zc-grid { display: grid; }
.zc-gap-sm { gap: var(--zc-space-sm); }
.zc-gap-md { gap: var(--zc-space-md); }


/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 768px) {
  .zc-module {
    padding: var(--zc-space-md);
  }

  .zc-module-header__title {
    font-size: var(--zc-fs-2xl);
  }

  .zc-module-header__meta {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--zc-space-sm);
  }

  .zc-heading--h2 {
    font-size: var(--zc-fs-xl);
  }

  .zc-heading--h3 {
    font-size: var(--zc-fs-lg);
  }

  .zc-stat__value {
    font-size: var(--zc-fs-3xl);
  }

  .zc-nav {
    flex-direction: column;
    gap: var(--zc-space-sm);
  }

  .zc-nav__btn {
    width: 100%;
    justify-content: center;
  }

  .zc-tabs__tab {
    padding: var(--zc-space-sm) var(--zc-space-md);
    font-size: var(--zc-fs-xs);
  }
}

@media (max-width: 480px) {
  .zc-module {
    padding: var(--zc-space-sm);
  }

  .zc-infobox {
    padding-left: var(--zc-space-md);
    padding-top: calc(var(--zc-space-md) + 28px);
  }

  .zc-infobox__icon {
    top: var(--zc-space-md);
    left: var(--zc-space-md);
  }

  .zc-stat-group {
    grid-template-columns: 1fr 1fr;
  }

  .zc-quiz-option {
    padding: var(--zc-space-sm) var(--zc-space-md);
    font-size: var(--zc-fs-sm);
  }

  .zc-quiz-option__letter {
    width: 24px;
    height: 24px;
    font-size: var(--zc-fs-xs);
  }

  .zc-code__body {
    padding: var(--zc-space-sm);
  }

  .zc-code__body pre {
    font-size: var(--zc-fs-xs);
  }

  .zc-accordion__trigger {
    padding: var(--zc-space-sm) var(--zc-space-md);
    font-size: var(--zc-fs-sm);
  }
}

/* Extra small — 375px mobile */
@media (max-width: 375px) {
  .zc-module {
    padding: var(--zc-space-xs);
  }

  .zc-module-header__title {
    font-size: var(--zc-fs-xl);
  }

  .zc-heading--h2 {
    font-size: var(--zc-fs-lg);
  }

  .zc-heading--h3 {
    font-size: var(--zc-fs-base);
  }

  .zc-stat__value {
    font-size: var(--zc-fs-2xl);
  }

  .zc-stat-group {
    grid-template-columns: 1fr;
  }

  .zc-comparison {
    font-size: var(--zc-fs-xs);
  }

  .zc-tabs__tab {
    min-width: 0;
    padding: var(--zc-space-xs) var(--zc-space-sm);
    font-size: 0.7rem;
  }

  .zc-exercise__steps {
    margin-bottom: var(--zc-space-md);
  }

  .zc-timeline {
    padding-left: var(--zc-space-lg);
  }
}


/* ============================================================
   ANIMATIONS
   ============================================================ */
@keyframes zcSlideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes zcPulse {
  0%, 100% { opacity: 1; }
  50%      { opacity: 0.7; }
}

@keyframes zcBarGrow {
  from { transform: scaleY(0); }
  to   { transform: scaleY(1); }
}

/* --- Markdown Table Styles --- */
.zc-text table, .zc-table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--zc-space-md) 0 var(--zc-space-lg) 0;
  font-size: var(--zc-fs-sm);
  border: 1px solid var(--zc-border);
  border-radius: var(--zc-radius-sm);
  overflow: hidden;
}

.zc-text table thead, .zc-table thead {
  background: var(--zc-card2);
}

.zc-text table th, .zc-table th {
  padding: var(--zc-space-sm) var(--zc-space-md);
  text-align: left;
  font-weight: 600;
  color: #fff;
  border-bottom: 2px solid var(--zc-border);
  font-size: var(--zc-fs-xs);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.zc-text table td, .zc-table td {
  padding: var(--zc-space-sm) var(--zc-space-md);
  border-bottom: 1px solid rgba(30, 30, 46, 0.5);
  color: var(--zc-text);
}

.zc-text table tr:last-child td, .zc-table tr:last-child td {
  border-bottom: none;
}

.zc-text table tr:hover td, .zc-table tr:hover td {
  background: rgba(99, 102, 241, 0.03);
}

/* --- Confetti Container --- */
.zc-confetti {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 9999;
  overflow: hidden;
}

.zc-confetti-piece {
  position: absolute;
  width: 8px;
  height: 8px;
  animation: zcConfettiFall 2.5s ease-in forwards;
  opacity: 0;
}

@keyframes zcConfettiFall {
  0% {
    opacity: 1;
    transform: translateY(-10vh) rotate(0deg);
  }
  100% {
    opacity: 0;
    transform: translateY(100vh) rotate(720deg);
  }
}

/* --- Smooth Scroll Target Highlight --- */
.zc-scroll-target {
  animation: zcHighlight 1.5s ease;
}

@keyframes zcHighlight {
  0% { box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.4); }
  100% { box-shadow: 0 0 0 0 rgba(99, 102, 241, 0); }
}

/* --- Chart Tooltip --- */
.zc-chart-tooltip {
  position: absolute;
  padding: 6px 12px;
  background: rgba(10, 10, 15, 0.92);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border: 1px solid var(--zc-border);
  border-radius: 6px;
  color: #fff;
  font-size: var(--zc-fs-xs);
  font-weight: 500;
  pointer-events: none;
  white-space: nowrap;
  z-index: 100;
  opacity: 0;
  transition: opacity var(--zc-transition-fast);
  transform: translate(-50%, -100%);
  margin-top: -8px;
}

.zc-chart-tooltip--visible {
  opacity: 1;
}

/* --- Keyboard Navigation Indicator --- */
.zc-quiz-option.zc-kbd-focus {
  border-color: var(--zc-accent);
  box-shadow: 0 0 0 2px rgba(99, 102, 241, 0.3);
  background: rgba(99, 102, 241, 0.04);
}

/* Print styles */
@media print {
  .zc-module {
    background: #fff;
    color: #111;
    max-width: 100%;
    padding: 0;
    font-size: 11pt;
    line-height: 1.5;
  }

  .zc-module * {
    color-adjust: exact;
    -webkit-print-color-adjust: exact;
    print-color-adjust: exact;
  }

  .zc-code__copy,
  .zc-nav,
  .zc-exercise__solution-toggle,
  .zc-checklist__checkbox,
  .zc-exercise__step-check,
  .zc-confetti {
    display: none !important;
  }

  .zc-module-header__title {
    color: #111;
    font-size: 18pt;
  }

  .zc-heading {
    color: #111;
    page-break-after: avoid;
  }

  .zc-text {
    color: #333;
  }

  .zc-text strong {
    color: #111;
  }

  .zc-infobox, .zc-keypoint, .zc-stat, .zc-quiz, .zc-exercise, .zc-code {
    break-inside: avoid;
    page-break-inside: avoid;
    border: 1px solid #ddd;
    background: #f9f9f9 !important;
    backdrop-filter: none !important;
  }

  .zc-infobox--tip { border-left: 3px solid #34d399; }
  .zc-infobox--warning { border-left: 3px solid #f59e0b; }
  .zc-infobox--danger { border-left: 3px solid #ef4444; }
  .zc-infobox--info { border-left: 3px solid #3b82f6; }

  .zc-code__body {
    background: #f4f4f4 !important;
  }

  .zc-code__body pre {
    color: #111;
    white-space: pre-wrap;
    word-wrap: break-word;
  }

  .zc-diagram svg {
    max-width: 100%;
    max-height: 300px;
  }

  .zc-section--collapsed .zc-section__body {
    max-height: none !important;
    opacity: 1 !important;
  }

  .zc-quiz-feedback,
  .zc-exercise__solution {
    max-height: none !important;
    display: block !important;
  }

  .zc-source__title a::after {
    content: " (" attr(href) ")";
    font-size: 9pt;
    color: #666;
  }

  .zc-text a::after {
    content: " [" attr(href) "]";
    font-size: 9pt;
    color: #666;
  }

  .zc-badge {
    border: 1px solid #ccc;
    background: transparent !important;
    color: #333 !important;
  }

  .zc-stat__value {
    background: none !important;
    -webkit-text-fill-color: #111 !important;
    color: #111 !important;
  }

  .zc-module-progress, .zc-progress, .zc-checklist__progress {
    display: none;
  }
}