/* ============================================================
   NEUROCIENCIAS — De la célula a la mente
   Sistema de diseño v1.0
   ============================================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=DM+Serif+Display:ital@0;1&family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* --- CSS Variables (semantic) --- */
:root {
  /* --- Premium Dark Palette --- */
  --color-primary: #0f172a;
  --color-primary-light: #1e293b;
  --color-primary-dark: #020617;
  --color-accent: #3b82f6; /* Azul Eléctrico */
  --color-accent-secondary: #2dd4bf; /* Cyan/Teal */
  --color-accent-light: #60a5fa;
  --color-accent-dark: #2563eb;
  --color-gold: #fde047;
  --color-gold-light: #fef08a;
  --color-gray: #64748b;
  --color-gray-light: #94a3b8;
  --color-gray-dark: #334155;

  /* --- Backgrounds --- */
  --bg-dark: #0b0f19;
  --bg-deep: #020617;
  --bg-card: rgba(30, 41, 59, 0.5);
  --bg-glass: rgba(15, 23, 42, 0.8);
  --bg-hero-overlay: rgba(2, 6, 23, 0.7);

  /* --- Text --- */
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-light: #f8fafc;
  --text-muted: #64748b;
  --text-on-accent: #ffffff;
  --text-on-dark: #f8fafc;

  /* --- Typography --- */
  --font-display: 'DM Serif Display', Georgia, serif;
  --font-body: 'Inter', -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Font sizes (fluid) */
  --fs-hero: clamp(2.4rem, 5vw, 4rem);
  --fs-h1: clamp(1.8rem, 3.5vw, 2.8rem);
  --fs-h2: clamp(1.4rem, 2.5vw, 2rem);
  --fs-h3: clamp(1.1rem, 2vw, 1.4rem);
  --fs-body: clamp(0.95rem, 1.2vw, 1.08rem);
  --fs-small: clamp(0.8rem, 1vw, 0.9rem);
  --fs-mono: 0.88rem;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  /* Layout */
  --max-width: 1440px;
  --content-width: 720px;
  --sidebar-width: 380px;
  --panel-width: 420px;

  /* Borders & Radii */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 20px;
  --border-thin: 1px solid rgba(255, 255, 255, 0.1);
  --border-accent: 2px solid var(--color-accent);

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.5);
  --shadow-panel: -4px 0 20px rgba(0, 0, 0, 0.4);

  /* Transitions */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --duration-fast: 150ms;
  --duration-normal: 300ms;
  --duration-slow: 500ms;

  /* Z-index layers */
  --z-sticky: 100;
  --z-panel: 150;
  --z-overlay: 160;
  --z-modal: 200;
  --z-toast: 300;
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--bg-dark);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

/* Grain texture overlay */
body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 9999;
  opacity: 0.025;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

img { max-width: 100%; display: block; }
a { color: var(--color-accent); text-decoration: none; transition: color var(--duration-fast); }
a:hover { color: var(--color-accent-dark); }

/* --- Typography --- */
h1, h2, h3 { font-family: var(--font-display); font-weight: 400; line-height: 1.2; color: var(--text-primary); }
h1 { font-size: var(--fs-h1); margin-bottom: var(--space-lg); }
h2 { font-size: var(--fs-h2); margin-bottom: var(--space-md); }
h3 { font-size: var(--fs-h3); margin-bottom: var(--space-sm); }

p { margin-bottom: var(--space-md); max-width: 65ch; }
strong { font-weight: 600; color: var(--color-primary); }

code, .mono {
  font-family: var(--font-mono);
  font-size: var(--fs-mono);
  background: rgba(26, 39, 68, 0.06);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
}

.term {
  font-weight: 600;
  color: var(--color-primary);
  border-bottom: 2px solid var(--color-gold);
  cursor: help;
}

/* --- Hero Section --- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: var(--space-2xl);
  background: var(--bg-dark);
  color: var(--text-light);
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 50%, var(--color-primary-light) 100%);
  z-index: 0;
}

.hero > * { position: relative; z-index: 1; }
.hero h1 { font-size: var(--fs-hero); color: var(--text-light); margin-bottom: var(--space-md); }
.hero .subtitle { font-size: var(--fs-h3); color: var(--color-gold); font-family: var(--font-display); font-style: italic; }
.hero .unit-number {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-accent-light);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-md);
  padding: var(--space-xs) var(--space-md);
  border: 1px solid rgba(232, 93, 74, 0.3);
  border-radius: var(--radius-sm);
}

/* --- Two-Panel Layout --- */
.two-panel {
  display: grid;
  grid-template-columns: 1fr 1fr;
  min-height: 100vh;
  max-width: var(--max-width);
  margin: 0 auto;
}

.panel-text {
  padding: var(--space-2xl) var(--space-xl);
  overflow-y: auto;
}

.panel-viz {
  position: sticky;
  top: 0;
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: var(--space-xl);
  background: var(--bg-card);
  border-left: var(--border-thin);
}

.panel-viz-content {
  width: 100%;
  max-width: 560px;
}

/* --- Section --- */
.section {
  padding: var(--space-3xl) 0;
  border-bottom: var(--border-thin);
}

.section:last-child { border-bottom: none; }

.section-label {
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-accent);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: var(--space-sm);
}

/* --- Cards --- */
.card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  border: var(--border-thin);
  transition: box-shadow var(--duration-normal) var(--ease-out), transform var(--duration-normal) var(--ease-out);
}

.card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.card-accent {
  border-left: 3px solid var(--color-accent);
}

.card-gold {
  border-left: 3px solid var(--color-gold);
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.7em 1.4em;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast);
  text-decoration: none;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--text-on-accent);
}
.btn-primary:hover {
  background: var(--color-accent-dark);
  color: var(--text-on-accent);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}
.btn-secondary:hover {
  background: var(--color-primary);
  color: var(--text-light);
}

.btn-ghost {
  background: transparent;
  color: var(--color-accent);
  padding: 0.5em 0.8em;
}
.btn-ghost:hover { background: rgba(232, 93, 74, 0.08); }

/* --- Side Panel (slide-out) --- */
.side-panel-overlay {
  position: fixed;
  inset: 0;
  background: rgba(26, 39, 68, 0.4);
  z-index: var(--z-overlay);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--duration-normal) var(--ease-out);
}

.side-panel-overlay.active {
  opacity: 1;
  pointer-events: all;
}

.side-panel {
  position: fixed;
  top: 0;
  right: 0;
  width: min(var(--panel-width), 90vw);
  height: 100vh;
  background: var(--bg-card);
  z-index: var(--z-panel);
  transform: translateX(100%);
  transition: transform var(--duration-slow) var(--ease-out);
  box-shadow: var(--shadow-panel);
  overflow-y: auto;
  padding: var(--space-xl);
}

.side-panel.active { transform: translateX(0); }

.side-panel-close {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  width: 36px;
  height: 36px;
  border: none;
  background: rgba(26, 39, 68, 0.06);
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  color: var(--text-secondary);
  transition: background var(--duration-fast);
}

.side-panel-close:hover { background: rgba(232, 93, 74, 0.1); color: var(--color-accent); }

.panel-trigger {
  display: inline-flex;
  align-items: center;
  gap: 0.3em;
  color: var(--color-accent);
  font-weight: 500;
  cursor: pointer;
  border-bottom: 1px dashed var(--color-accent-light);
  transition: color var(--duration-fast);
}

.panel-trigger:hover { color: var(--color-accent-dark); }
.panel-trigger::after { content: '→'; font-size: 0.85em; }

/* --- Quiz System --- */
.quiz {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
  border: var(--border-thin);
}

.quiz-question {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  margin-bottom: var(--space-lg);
}

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

.quiz-option {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-warm);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast);
  font-size: var(--fs-body);
}

.quiz-option:hover { border-color: var(--color-gray-light); background: var(--bg-warm-alt); }
.quiz-option.selected { border-color: var(--color-primary); background: rgba(26, 39, 68, 0.05); }
.quiz-option.correct { border-color: #4caf50; background: rgba(76, 175, 80, 0.08); }
.quiz-option.incorrect { border-color: var(--color-accent); background: rgba(232, 93, 74, 0.06); }

.quiz-option-letter {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--color-primary);
  color: var(--text-light);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  font-weight: 600;
}

.quiz-feedback {
  margin-top: var(--space-lg);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  font-size: var(--fs-body);
  display: none;
}

.quiz-feedback.show { display: block; }
.quiz-feedback.correct { background: rgba(76, 175, 80, 0.1); border-left: 3px solid #4caf50; }
.quiz-feedback.incorrect { background: rgba(232, 93, 74, 0.1); border-left: 3px solid var(--color-accent); }

.quiz-submit {
  margin-top: var(--space-md);
}

/* --- Checklist (persistent) --- */
.checklist {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  border: var(--border-thin);
}

.checklist-title {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.checklist-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-sm) 0;
  border-bottom: 1px solid rgba(26, 39, 68, 0.05);
}

.checklist-item:last-child { border-bottom: none; }

.checklist-checkbox {
  flex-shrink: 0;
  width: 22px;
  height: 22px;
  border: 2px solid var(--color-gray-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--duration-fast);
  background: transparent;
}

.checklist-checkbox.checked {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: white;
}

.checklist-checkbox.checked::after { content: '✓'; font-size: 0.8rem; color: white; }

.checklist-label { font-size: var(--fs-body); }
.checklist-label.checked { text-decoration: line-through; color: var(--text-muted); }

.checklist-progress {
  margin-top: var(--space-md);
  height: 4px;
  background: rgba(26, 39, 68, 0.08);
  border-radius: 2px;
  overflow: hidden;
}

.checklist-progress-bar {
  height: 100%;
  background: var(--color-accent);
  border-radius: 2px;
  transition: width var(--duration-normal) var(--ease-out);
}

/* --- Interactive SVG areas --- */
.interactive-image {
  position: relative;
  width: 100%;
}

.interactive-image svg { width: 100%; height: auto; }

.hotspot {
  cursor: pointer;
  transition: all var(--duration-fast);
}

.hotspot:hover { filter: brightness(1.1); }
.hotspot.active { filter: brightness(1.2); stroke: var(--color-accent); stroke-width: 2; }

.hotspot-label {
  position: absolute;
  background: var(--color-primary);
  color: var(--text-light);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  font-size: var(--fs-small);
  font-family: var(--font-mono);
  pointer-events: none;
  white-space: nowrap;
  transform: translate(-50%, -100%);
  margin-top: -8px;
  opacity: 0;
  transition: opacity var(--duration-fast);
}

.hotspot-label.visible { opacity: 1; }

/* --- Navigation --- */
.nav-top {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 56px;
  background: rgba(245, 240, 232, 0.95);
  backdrop-filter: blur(12px);
  border-bottom: var(--border-thin);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-xl);
  z-index: var(--z-sticky);
}

.nav-brand {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--color-primary);
}

.nav-links {
  display: flex;
  gap: var(--space-lg);
  align-items: center;
}

.nav-link {
  font-size: var(--fs-small);
  color: var(--text-secondary);
  font-weight: 500;
  transition: color var(--duration-fast);
}

.nav-link:hover { color: var(--color-accent); }
.nav-link.active { color: var(--color-accent); }

/* Unit navigation */
.unit-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xl);
  margin-top: var(--space-2xl);
  border-top: var(--border-thin);
}

.unit-nav-link {
  display: flex;
  flex-direction: column;
  gap: 0.2em;
  text-decoration: none;
}

.unit-nav-label {
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.unit-nav-title {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
}

.unit-nav-link:hover .unit-nav-title { color: var(--color-accent); }

/* --- Landing Page --- */
.landing-hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: var(--space-2xl);
  background: linear-gradient(160deg, var(--color-primary-dark) 0%, var(--color-primary) 40%, var(--color-primary-light) 100%);
  color: var(--text-light);
  position: relative;
}

.course-title {
  font-family: var(--font-display);
  font-size: clamp(2.5rem, 6vw, 5rem);
  color: var(--text-light);
  margin-bottom: var(--space-md);
  line-height: 1.1;
}

.course-subtitle {
  font-family: var(--font-display);
  font-style: italic;
  font-size: var(--fs-h2);
  color: var(--color-gold);
  margin-bottom: var(--space-xl);
}

.block-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: var(--space-xl);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-xl);
}

.block-card {
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  box-shadow: var(--shadow-sm);
  border: var(--border-thin);
}

.block-card h2 {
  font-size: var(--fs-h2);
  margin-bottom: var(--space-sm);
}

.block-number {
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-accent);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-sm);
}

.unit-list { list-style: none; }

.unit-list-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) 0;
  border-bottom: 1px solid rgba(26, 39, 68, 0.06);
}

.unit-list-item:last-child { border-bottom: none; }

.unit-list-number {
  flex-shrink: 0;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--bg-warm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  font-weight: 600;
  color: var(--color-primary);
}

.unit-list-item a {
  color: var(--text-primary);
  font-weight: 500;
  transition: color var(--duration-fast);
}

.unit-list-item a:hover { color: var(--color-accent); }

/* --- Progress indicator --- */
.progress-bar-container {
  position: fixed;
  top: 56px;
  left: 0;
  right: 0;
  height: 3px;
  background: rgba(26, 39, 68, 0.06);
  z-index: var(--z-sticky);
}

.progress-bar-fill {
  height: 100%;
  background: var(--color-accent);
  width: 0%;
  transition: width 100ms linear;
}

/* --- Drag & Drop --- */
.drag-zone {
  min-height: 60px;
  border: 2px dashed var(--color-gray-light);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  transition: border-color var(--duration-fast), background var(--duration-fast);
}

.drag-zone.drag-over {
  border-color: var(--color-accent);
  background: rgba(232, 93, 74, 0.04);
}

.drag-item {
  display: inline-flex;
  align-items: center;
  padding: var(--space-xs) var(--space-md);
  background: var(--color-primary);
  color: var(--text-light);
  border-radius: var(--radius-md);
  font-size: var(--fs-small);
  font-weight: 500;
  cursor: grab;
  user-select: none;
  transition: transform var(--duration-fast), box-shadow var(--duration-fast);
}

.drag-item:active { cursor: grabbing; transform: scale(1.05); box-shadow: var(--shadow-md); }
.drag-item.correct { background: #4caf50; }
.drag-item.incorrect { background: var(--color-accent); }

/* --- Tooltip --- */
.tooltip {
  position: relative;
}

.tooltip-content {
  position: absolute;
  bottom: calc(100% + 8px);
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-primary);
  color: var(--text-light);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  font-size: var(--fs-small);
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--duration-fast);
  z-index: var(--z-toast);
}

.tooltip:hover .tooltip-content { opacity: 1; }

/* --- Session Tabs --- */
.session-tabs {
  display: flex;
  gap: 2px;
  background: rgba(26, 39, 68, 0.06);
  border-radius: var(--radius-md);
  padding: 3px;
  margin-bottom: var(--space-xl);
}

/* --- Standard Session Tabs (Used in Units) --- */
.session-tabs, .session-tabs-container {
  display: flex;
  gap: 15px;
  margin-bottom: var(--space-xl);
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  padding-bottom: 5px;
}

.session-tab, .tab-button {
  flex: 1;
  padding: 12px 20px;
  text-align: center;
  font-family: var(--font-body);
  font-size: var(--fs-small);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: all var(--duration-normal) var(--ease-out);
}

.session-tab:hover, .tab-button:hover { 
  color: var(--text-primary); 
}

.session-tab.active, .tab-button.active {
  color: var(--color-accent);
  border-bottom: 2px solid var(--color-accent);
  background: rgba(59, 130, 246, 0.05);
}

.session-content { display: none; }
.session-content.active { display: block; }

/* --- Responsive --- */
@media (max-width: 1024px) {
  .two-panel {
    grid-template-columns: 1fr;
  }

  .panel-viz {
    position: relative;
    height: auto;
    min-height: 50vh;
    border-left: none;
    border-top: var(--border-thin);
  }

  .block-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  .hero { min-height: 80vh; padding: var(--space-xl); }
  .panel-text { padding: var(--space-lg); }
  .panel-viz { padding: var(--space-lg); min-height: 40vh; }
  .nav-top { padding: 0 var(--space-md); }
  .unit-nav { flex-direction: column; gap: var(--space-lg); }
  .side-panel { width: 100vw; }
}

@media (max-width: 375px) {
  :root {
    --space-xl: 1.5rem;
    --space-2xl: 2.5rem;
  }
}

/* --- Utility classes --- */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

.text-center { text-align: center; }
.text-accent { color: var(--color-accent); }
.text-gold { color: var(--color-gold); }
.text-muted { color: var(--text-muted); }
.mt-xl { margin-top: var(--space-xl); }
.mb-xl { margin-bottom: var(--space-xl); }
.fade-in { animation: fadeIn var(--duration-slow) var(--ease-out); }

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(20px); }
  to { opacity: 1; transform: translateX(0); }
}

.slide-in { animation: slideInRight var(--duration-slow) var(--ease-out); }

/* ============================================================
   GLOBAL PREMIUM COMPONENTS (Unified Course Design)
   ============================================================ */

/* --- Navigation (Global-Nav Glassmorphism) --- */
.global-nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 20px 40px;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: var(--z-sticky);
    transition: all 0.4s var(--ease-out);
}

.global-nav.scrolled,
.global-nav.always-dark {
    padding: 12px 40px;
    background: var(--bg-glass);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.global-nav .nav-container {
    width: 100%;
    max-width: var(--max-width);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-family: var(--font-display);
    font-size: 1.4rem;
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 400;
    letter-spacing: 0.5px;
}

.nav-links {
    display: flex;
    gap: 30px;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.3s ease;
    letter-spacing: 0.5px;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--color-accent);
}

.btn-nav-recursos {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    padding: 8px 20px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.btn-nav-recursos:hover {
    background: var(--color-accent);
    border-color: var(--color-accent);
    color: white;
}

/* --- Premium Buttons --- */
.btn-premium {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    background: var(--color-accent);
    color: white;
    border: none;
    padding: 12px 28px;
    border-radius: 30px;
    font-family: var(--font-body);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.btn-premium:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(59, 130, 246, 0.4);
    background: var(--color-accent-dark);
}

.btn-premium-outline {
    background: transparent;
    border: 2px solid var(--color-accent);
    color: var(--color-accent);
}

.btn-premium-outline:hover {
    background: var(--color-accent);
    color: white;
}

/* --- Premium Hero Section (Standardized Units) --- */
.premium-hero {
    position: relative;
    width: 100%;
    min-height: 45vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 120px 20px 60px;
    background: var(--bg-deep);
    overflow: hidden;
}

.hero-bg-glow {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(59, 130, 246, 0.1) 0%, transparent 70%);
    pointer-events: none;
    z-index: 1;
}

.premium-hero h1 {
    font-size: var(--fs-hero);
    color: var(--text-primary);
    margin: 0;
    z-index: 2;
    letter-spacing: -0.5px;
}

.premium-hero h2 {
    font-family: var(--font-body);
    font-size: var(--fs-h3);
    color: var(--color-accent);
    font-weight: 500;
    margin: 10px 0 20px;
    z-index: 2;
    letter-spacing: 1px;
    text-transform: uppercase;
}

.premium-hero .hero-desc {
    max-width: 600px;
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin: 0 auto;
    z-index: 2;
}

/* --- Premium Cards --- */
.premium-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-lg);
    padding: 30px;
    transition: all 0.3s var(--ease-out);
}

.premium-card:hover {
    transform: translateY(-5px);
    border-color: rgba(59, 130, 246, 0.3);
    background: rgba(30, 41, 59, 0.8);
}

/* --- Navbar --- */
.navbar {
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  background: rgba(26, 39, 68, 0.97);
  backdrop-filter: blur(12px);
  padding: 0 var(--space-xl);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  min-height: 56px;
  color: var(--text-light);
}

.navbar .nav-content,
.navbar .nav-container,
.navbar .navbar-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
}

.navbar .nav-title,
.navbar .nav-logo,
.navbar .navbar-title,
.navbar .navbar-brand h2 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--text-light);
  margin: 0;
}

.navbar .nav-links,
.navbar .nav-menu,
.navbar .navbar-menu {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
  align-items: center;
  margin: 0;
  padding: 0;
}

.navbar .nav-links a,
.navbar .nav-menu a,
.navbar .navbar-menu a {
  color: var(--text-on-dark);
  font-size: var(--fs-small);
  font-weight: 500;
  opacity: 0.8;
  transition: opacity var(--duration-fast);
}

.navbar .nav-links a:hover,
.navbar .nav-menu a:hover,
.navbar .navbar-menu a:hover { opacity: 1; color: var(--color-gold); }

.navbar .progress-bar {
  width: 100%;
  height: 3px;
  background: rgba(255,255,255,0.1);
  border-radius: 2px;
  overflow: hidden;
}

.navbar .progress-bar .progress-fill,
.progress-container .progress-bar {
  height: 100%;
  background: var(--color-accent);
  border-radius: 2px;
  transition: width 300ms ease;
}

/* --- Progress Container (standalone) --- */
.progress-container {
  height: 4px;
  background: rgba(26, 39, 68, 0.08);
  position: sticky;
  top: 56px;
  z-index: var(--z-sticky);
}

/* --- Hero adjustments for unit pages --- */
.hero {
  min-height: 40vh;
}

.hero-label,
.hero .unit-number {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-accent-light);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-sm);
  padding: var(--space-xs) var(--space-md);
  border: 1px solid rgba(232, 93, 74, 0.3);
  border-radius: var(--radius-sm);
}

.hero h2,
.hero-subtitle {
  font-family: var(--font-display);
  font-style: italic;
  font-size: var(--fs-h2);
  color: var(--color-gold);
  margin-bottom: var(--space-md);
}

.hero-description {
  font-size: var(--fs-body);
  color: var(--text-on-dark);
  opacity: 0.85;
  max-width: 600px;
}

.hero .progress-bar {
  width: 200px;
  height: 4px;
  background: rgba(255,255,255,0.15);
  border-radius: 2px;
  margin-top: var(--space-lg);
  overflow: hidden;
}

.hero .progress-fill {
  height: 100%;
  background: var(--color-accent);
  border-radius: 2px;
}

/* --- Session Tabs (tab-button variant) --- */
.session-tabs-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-xl) 0;
}

.tab-button {
  flex: 1;
  padding: var(--space-sm) var(--space-md);
  text-align: center;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  font-weight: 500;
  color: var(--text-secondary);
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--duration-fast);
}

.tab-button:hover { color: var(--color-primary); }
.tab-button.active {
  background: var(--bg-card);
  color: var(--color-accent);
  box-shadow: var(--shadow-sm);
}

/* --- Main Content Containers --- */
.main-content, .container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-xl);
}

.content-wrapper,
.main-wrapper {
  display: grid;
  grid-template-columns: 1fr minmax(250px, 340px);
  gap: var(--space-xl);
  align-items: start;
}

@media (max-width: 1024px) {
  .content-wrapper,
  .main-wrapper {
    grid-template-columns: 1fr;
  }
}

/* --- Main Panel --- */
.main-panel {
  min-width: 0;
}

/* --- Side Panels (inline, non-overlay variant for units 1.2–1.4) --- */
.content-wrapper .side-panels,
.main-wrapper .side-panels {
  position: sticky;
  top: 70px;
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  max-height: calc(100vh - 90px);
  overflow-y: auto;
}

.content-wrapper .side-panel,
.main-wrapper .side-panel {
  position: static;
  transform: none;
  width: auto;
  height: auto;
  box-shadow: none;
  padding: var(--space-lg);
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  border-left: 3px solid var(--color-gold);
  overflow: visible;
}

.content-wrapper .side-panel h4,
.content-wrapper .side-panel h5,
.main-wrapper .side-panel h4,
.main-wrapper .side-panel h5,
.side-panel .panel-title {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  margin-bottom: var(--space-sm);
}

.content-wrapper .side-panel p,
.main-wrapper .side-panel p {
  font-size: var(--fs-small);
  color: var(--text-secondary);
  line-height: 1.6;
}

.content-wrapper .side-panel dl {
  margin: 0;
}

.content-wrapper .side-panel dt {
  font-weight: 600;
  color: var(--color-primary);
  margin-top: var(--space-sm);
}

.content-wrapper .side-panel dd {
  margin-left: 0;
  color: var(--text-secondary);
  font-size: var(--fs-small);
  padding-bottom: var(--space-sm);
  border-bottom: 1px solid rgba(26, 39, 68, 0.06);
}

/* Panel active state for clickable side panels (1.4) */
.side-panel.panel-active {
  border-left-color: var(--color-accent);
}

/* --- Content Sections & Articles --- */
.content-section,
article.section {
  padding: var(--space-xl) 0;
  border-bottom: var(--border-thin);
}

.content-section:last-child,
article.section:last-child { border-bottom: none; }

.content-section h3,
article.section h4,
.section-title {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.section-text {
  line-height: 1.8;
  margin-bottom: var(--space-md);
}

.content-subsection {
  margin: var(--space-lg) 0;
  padding-left: var(--space-lg);
  border-left: 2px solid var(--color-gold-light);
}

.content-subsection h4 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: var(--color-primary);
  margin-bottom: var(--space-sm);
}

.content-subsection ul {
  padding-left: var(--space-lg);
  margin-bottom: var(--space-md);
}

.content-subsection li {
  margin-bottom: var(--space-sm);
  line-height: 1.7;
}

.session-title {
  font-family: var(--font-display);
  font-size: var(--fs-h2);
  color: var(--color-primary);
  margin-bottom: var(--space-xl);
  padding-bottom: var(--space-md);
  border-bottom: 2px solid var(--color-accent);
}

/* --- Interactive Section (SVG diagrams) --- */
.interactive-section {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
}

.interactive-section h4,
.interactive-section h3 {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.brain-svg,
.synapse-svg {
  width: 100%;
  max-width: 550px;
  height: auto;
  margin: 0 auto;
  display: block;
  cursor: pointer;
}

.interactive-structure {
  cursor: pointer;
  transition: opacity var(--duration-fast), filter var(--duration-fast);
}

.interactive-structure:hover {
  opacity: 0.85;
  filter: brightness(1.15);
}

.brain-label {
  font-size: 11px;
  font-weight: bold;
  pointer-events: none;
  transition: opacity 0.2s;
  fill: var(--color-primary);
}

.caption {
  text-align: center;
  font-size: var(--fs-small);
  color: var(--text-muted);
  margin-top: var(--space-sm);
  font-style: italic;
}

.info-box {
  background-color: rgba(26, 39, 68, 0.04);
  border-left: 4px solid var(--color-primary);
  padding: var(--space-lg);
  margin: var(--space-lg) 0;
  border-radius: var(--radius-md);
  animation: fadeIn var(--duration-normal) var(--ease-out);
}

.info-box h5 {
  margin: 0 0 var(--space-sm) 0;
  color: var(--color-primary);
  font-family: var(--font-display);
}

.close-btn {
  background-color: var(--color-primary);
  color: var(--text-light);
  border: none;
  padding: var(--space-xs) var(--space-md);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: var(--fs-small);
  margin-top: var(--space-sm);
  transition: background var(--duration-fast);
}

.close-btn:hover { background-color: var(--color-accent); }

/* --- Practice Components --- */
.practice-container,
.practice-exercises {
  display: grid;
  gap: var(--space-xl);
  margin: var(--space-lg) 0;
}

.structures-box,
.match-box {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
}

.structures-box h5,
.match-box h5 {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.draggable-area {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.structure-item {
  display: inline-flex;
  align-items: center;
  padding: var(--space-sm) var(--space-md);
  background: var(--color-primary);
  color: var(--text-light);
  border-radius: var(--radius-md);
  font-size: var(--fs-small);
  font-weight: 500;
  cursor: grab;
  user-select: none;
  transition: transform var(--duration-fast), box-shadow var(--duration-fast);
}

.structure-item:active { cursor: grabbing; transform: scale(1.05); box-shadow: var(--shadow-md); }

.matching-area {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.function-item {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md);
  background: var(--bg-warm);
  border-radius: var(--radius-md);
}

.function-text {
  flex: 1;
  min-width: 200px;
  font-weight: 500;
}

.match-select {
  padding: var(--space-sm) var(--space-md);
  border: 2px solid var(--color-gray-light);
  border-radius: var(--radius-sm);
  font-family: var(--font-body);
  font-size: var(--fs-small);
  background: white;
  cursor: pointer;
  transition: border-color var(--duration-fast);
}

.match-select:focus { border-color: var(--color-accent); outline: none; }

.feedback {
  padding: var(--space-md);
  border-radius: var(--radius-md);
  margin-top: var(--space-md);
  font-weight: 500;
}

.feedback-correct { color: #2e7d32; }
.feedback-incorrect { color: var(--color-accent); }

/* --- Practice Builder (ordering steps) --- */
.practice-builder {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
  margin: var(--space-lg) 0;
}

@media (max-width: 768px) {
  .practice-builder { grid-template-columns: 1fr; }
}

.steps-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.step-card {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-card);
  border: 2px solid var(--color-gray-light);
  border-radius: var(--radius-md);
  cursor: grab;
  user-select: none;
  transition: all var(--duration-fast);
}

.step-card:hover { border-color: var(--color-primary); box-shadow: var(--shadow-sm); }
.step-card:active { cursor: grabbing; }

.step-number {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--color-primary);
  color: var(--text-light);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  font-weight: 600;
}

.step-text { font-weight: 500; }

.steps-workspace {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.steps-ordered {
  min-height: 200px;
  border: 2px dashed var(--color-gray-light);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  transition: border-color var(--duration-fast);
}

.steps-ordered .placeholder {
  color: var(--text-muted);
  text-align: center;
  padding: var(--space-xl);
  font-style: italic;
}

.feedback-hidden { display: none; }

.animation-container {
  margin-top: var(--space-xl);
}

.animation-container.hidden { display: none; }

/* --- Simulation Components --- */
.simulation-container {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin: var(--space-lg) 0;
}

.simulation-controls {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
}

.simulation-canvas {
  width: 100%;
  border-radius: var(--radius-md);
  border: var(--border-thin);
  background: var(--bg-card);
}

.simulation-info {
  display: flex;
  gap: var(--space-xl);
  margin-top: var(--space-md);
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--text-secondary);
  flex-wrap: wrap;
}

.toggle-label {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: var(--fs-small);
  cursor: pointer;
}

/* --- Quiz Components (form-based variant) --- */
.quiz-form,
.quiz-container {
  margin: var(--space-lg) 0;
}

.quiz-form .quiz-question,
.quiz-container .quiz-question {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.quiz-form .quiz-question label,
.quiz-container .question-text,
.quiz-container .quiz-question h4 {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  display: block;
  margin-bottom: var(--space-md);
}

.radio-group,
.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.radio-group label,
.quiz-options label,
.quiz-options .option,
.quiz-label,
.option-label {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-warm);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast);
  font-size: var(--fs-body);
}

.radio-group label:hover,
.quiz-options label:hover,
.quiz-label:hover,
.option-label:hover {
  border-color: var(--color-gray-light);
  background: var(--bg-warm-alt);
}

.radio-group input[type="radio"],
.quiz-options input[type="radio"] {
  accent-color: var(--color-accent);
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.quiz-results,
.quiz-result {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-top: var(--space-lg);
}

.quiz-result.hidden,
.quiz-result-hidden { display: none; }

.quiz-heading {
  font-family: var(--font-display);
  font-size: var(--fs-h2);
  color: var(--color-primary);
  margin-bottom: var(--space-lg);
}

.quiz-submit-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.7em 1.4em;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  background: var(--color-accent);
  color: var(--text-on-accent);
  transition: all var(--duration-fast);
  margin-top: var(--space-md);
}

.quiz-submit-btn:hover {
  background: var(--color-accent-dark);
  transform: translateY(-1px);
}

.result-content { font-size: var(--fs-body); }

/* --- Mastery Checklist --- */
.mastery-checklist {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-top: var(--space-xl);
}

.mastery-checklist h4,
.mastery-checklist h3,
.checklist-heading {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.mastery-checklist ul,
.checklist-items {
  list-style: none;
  padding: 0;
}

.mastery-checklist li,
.mastery-checklist label.checklist-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
  padding: var(--space-md) 0;
  border-bottom: 1px solid rgba(26, 39, 68, 0.06);
  cursor: pointer;
}

.mastery-checklist li:last-child,
.mastery-checklist label.checklist-item:last-child { border-bottom: none; }

.mastery-checklist input[type="checkbox"],
.checklist-checkbox {
  accent-color: var(--color-accent);
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  margin-top: 2px;
}

.assessment-note {
  text-align: center;
  color: var(--text-muted);
  font-style: italic;
  margin-top: var(--space-lg);
}

/* --- Unit Navigation Footer --- */
.unit-navigation {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-xl);
  margin-top: var(--space-2xl);
  border-top: var(--border-thin);
  max-width: var(--max-width);
  margin-left: auto;
  margin-right: auto;
}

.unit-navigation a,
.unit-nav-button,
.nav-link,
.nav-button {
  color: var(--color-accent);
  font-weight: 500;
  text-decoration: none;
  transition: color var(--duration-fast);
}

.unit-navigation a:hover,
.unit-nav-button:hover { color: var(--color-accent-dark); }

.unit-divider,
.nav-divider,
.unit-nav-current {
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: var(--fs-small);
}

.unit-navigation .nav-prev,
.unit-navigation .nav-next {
  display: flex;
  flex-direction: column;
  gap: 0.2em;
}

.unit-navigation .nav-prev a,
.unit-navigation .nav-next a {
  color: var(--color-accent);
  text-decoration: none;
}

.unit-navigation .nav-arrow {
  font-size: 1.2rem;
}

.unit-navigation .nav-text {
  font-weight: 500;
}

.unit-navigation .nav-progress {
  text-align: center;
}

.unit-label {
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--text-muted);
}

/* --- Footer --- */
.footer {
  text-align: center;
  padding: var(--space-xl);
  border-top: var(--border-thin);
  background: var(--bg-warm);
  color: var(--text-muted);
  font-size: var(--fs-small);
}

.footer-text { margin: 0; }

/* --- Practice Exercise (drag & drop) --- */
.practice-exercise {
  margin: var(--space-lg) 0;
}

.classification-zones {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-md);
  margin-bottom: var(--space-xl);
}

.drop-zone {
  min-height: 120px;
  border: 2px dashed var(--color-gray-light);
  border-radius: var(--radius-lg);
  padding: var(--space-md);
  text-align: center;
  transition: all var(--duration-fast);
}

.drop-zone:hover { border-color: var(--color-primary); }

.zone-title {
  font-family: var(--font-display);
  font-size: 1rem;
  color: var(--color-primary);
  margin-bottom: var(--space-sm);
}

.zone-hint {
  font-size: var(--fs-small);
  color: var(--text-muted);
  font-style: italic;
}

.zone-content {
  min-height: 40px;
}

.scenarios-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: var(--space-md);
  margin-bottom: var(--space-xl);
}

.scenario-card {
  background: var(--bg-card);
  border: 2px solid var(--color-gray-light);
  border-radius: var(--radius-md);
  padding: var(--space-md) var(--space-lg);
  cursor: grab;
  user-select: none;
  transition: all var(--duration-fast);
}

.scenario-card:hover { border-color: var(--color-accent); box-shadow: var(--shadow-sm); }
.scenario-card:active { cursor: grabbing; }

.scenario-text { font-weight: 500; }

.feedback-panel {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  margin-top: var(--space-lg);
}

.feedback-header {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  margin-bottom: var(--space-sm);
}

/* --- Synapse diagram --- */
.synapse-diagram-container {
  margin: var(--space-xl) 0;
  text-align: center;
}

.diagram-label {
  font-family: var(--font-body);
  font-size: 11px;
  fill: var(--color-primary);
}

.step-label {
  font-family: var(--font-mono);
  font-size: 11px;
  fill: var(--text-secondary);
}

.control-container {
  display: flex;
  gap: var(--space-md);
  justify-content: center;
  margin: var(--space-lg) 0;
  flex-wrap: wrap;
}

/* --- Drug Cards (1.4 practice) --- */
.drug-card {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.drug-name {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-xs);
}

.drug-description {
  color: var(--text-secondary);
  font-size: var(--fs-small);
  margin-bottom: var(--space-md);
  font-style: italic;
}

.drug-options {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}

/* --- Visualization container --- */
.viz-container {
  width: 100%;
  max-width: 400px;
}

.viz-hint {
  text-align: center;
  font-size: var(--fs-small);
  color: var(--text-muted);
  font-style: italic;
  margin-top: var(--space-sm);
}

.nervous-system-diagram {
  width: 100%;
  height: auto;
}

/* --- Side Panel (overlay variant for 1.1) --- */
.side-panels .side-panel[data-panel] {
  position: fixed;
  top: 0;
  right: 0;
  width: min(var(--panel-width), 90vw);
  height: 100vh;
  background: var(--bg-card);
  z-index: var(--z-panel);
  display: none;
  box-shadow: var(--shadow-panel);
  overflow-y: auto;
  padding: var(--space-xl);
}

.side-panels .panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-lg);
}

.side-panels .panel-header h3 {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin: 0;
}

.side-panels .panel-close {
  width: 36px;
  height: 36px;
  border: none;
  background: rgba(26, 39, 68, 0.06);
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.4rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--duration-fast);
}

.side-panels .panel-close:hover {
  background: rgba(232, 93, 74, 0.1);
  color: var(--color-accent);
}

.side-panels .panel-body {
  line-height: 1.8;
}

.side-panels .panel-body h4 {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin: var(--space-lg) 0 var(--space-sm);
}

.side-panels .panel-body ul {
  padding-left: var(--space-lg);
  margin-bottom: var(--space-md);
}

.side-panels .panel-body li {
  margin-bottom: var(--space-sm);
}

/* --- Quiz feedback inline --- */
.quiz-feedback {
  margin-top: var(--space-sm);
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-sm);
  font-size: var(--fs-small);
  font-weight: 500;
}

/* --- Buttons general adjustments --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.7em 1.4em;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast);
  text-decoration: none;
}

/* Ensure btn-primary and btn-secondary also work without .btn class */
button.btn-primary,
a.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.7em 1.4em;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  background: var(--color-accent);
  color: var(--text-on-accent);
  text-decoration: none;
  transition: all var(--duration-fast);
}

button.btn-primary:hover,
a.btn-primary:hover {
  background: var(--color-accent-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

button.btn-secondary,
a.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.7em 1.4em;
  border: 1px solid var(--color-primary);
  border-radius: var(--radius-md);
  cursor: pointer;
  background: transparent;
  color: var(--color-primary);
  text-decoration: none;
  transition: all var(--duration-fast);
}

button.btn-secondary:hover,
a.btn-secondary:hover {
  background: var(--color-primary);
  color: var(--text-light);
}

/* --- Accessibility & Polish --- */
*:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

::selection {
  background: rgba(232, 93, 74, 0.2);
  color: var(--color-primary);
}

/* Scrollbar styling */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(26, 39, 68, 0.15); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: rgba(26, 39, 68, 0.25); }

/* --- Illustration Images --- */
.illustration {
  display: block;
  max-width: 100%;
  margin: 1.5rem auto;
  border-radius: var(--radius-md, 8px);
  box-shadow: 0 2px 12px rgba(26, 39, 68, 0.1);
  border: 1px solid rgba(26, 39, 68, 0.08);
}
.illustration-caption {
  text-align: center;
  font-size: 0.85rem;
  color: var(--color-gray-dark, #5a5e62);
  margin-top: 0.5rem;
  margin-bottom: 1.5rem;
  font-style: italic;
}

/* ============================================================
   CLINICAL CASE CARDS
   ============================================================ */
.clinical-case {
  background: var(--bg-card);
  border: var(--border-thin);
  border-left: 4px solid var(--color-gold);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
  position: relative;
}

.clinical-case::before {
  content: 'CASO CLÍNICO';
  display: block;
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-gold);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-md);
  font-weight: 600;
}

.clinical-case h4 {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.clinical-case .case-narrative {
  font-style: italic;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: var(--space-lg);
  padding-left: var(--space-lg);
  border-left: 2px solid var(--color-gold-light);
}

.clinical-case .case-question {
  background: var(--bg-warm);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-md);
  font-weight: 500;
  color: var(--color-primary);
}

.clinical-case .case-answer {
  display: none;
  background: rgba(76, 175, 80, 0.06);
  border-left: 3px solid #4caf50;
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  margin-top: var(--space-md);
  line-height: 1.7;
}

.clinical-case .case-answer.visible {
  display: block;
  animation: fadeIn var(--duration-normal) var(--ease-out);
}

.clinical-case .case-reveal-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  font-weight: 500;
  padding: 0.5em 1.2em;
  border: 1px solid var(--color-gold);
  border-radius: var(--radius-md);
  cursor: pointer;
  background: transparent;
  color: var(--color-gold);
  transition: all var(--duration-fast);
}

.clinical-case .case-reveal-btn:hover {
  background: var(--color-gold);
  color: white;
}

/* ============================================================
   ENHANCED QUIZ SYSTEM (multi-question with feedback)
   ============================================================ */
.quiz-multi {
  margin: var(--space-xl) 0;
}

.quiz-multi .quiz-item {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.quiz-multi .quiz-item h4 {
  font-family: var(--font-display);
  font-size: var(--fs-h3);
  color: var(--color-primary);
  margin-bottom: var(--space-md);
}

.quiz-multi .quiz-item .quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.quiz-multi .quiz-item .quiz-option {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-warm);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast);
}

.quiz-multi .quiz-option:hover {
  border-color: var(--color-gray-light);
  background: var(--bg-warm-alt);
}

.quiz-multi .quiz-option.selected { border-color: var(--color-primary); }
.quiz-multi .quiz-option.correct { border-color: #4caf50; background: rgba(76, 175, 80, 0.08); }
.quiz-multi .quiz-option.incorrect { border-color: var(--color-accent); background: rgba(232, 93, 74, 0.06); }

.quiz-multi .quiz-option input[type="radio"] {
  accent-color: var(--color-accent);
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.quiz-multi .quiz-explanation {
  display: none;
  margin-top: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  font-size: var(--fs-small);
  line-height: 1.6;
}

.quiz-multi .quiz-explanation.show {
  display: block;
  animation: fadeIn var(--duration-normal) var(--ease-out);
}

.quiz-multi .quiz-explanation.correct {
  background: rgba(76, 175, 80, 0.08);
  border-left: 3px solid #4caf50;
}

.quiz-multi .quiz-explanation.incorrect {
  background: rgba(232, 93, 74, 0.06);
  border-left: 3px solid var(--color-accent);
}

.quiz-score-panel {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  text-align: center;
  margin-top: var(--space-lg);
  display: none;
}

.quiz-score-panel.visible {
  display: block;
  animation: fadeIn var(--duration-normal) var(--ease-out);
}

.quiz-score-panel .score-number {
  font-family: var(--font-display);
  font-size: var(--fs-h1);
  color: var(--color-accent);
  margin-bottom: var(--space-sm);
}

.quiz-score-panel .score-label {
  color: var(--text-secondary);
  font-size: var(--fs-body);
}

/* ============================================================
   INTERACTIVE EXERCISES (canvas-based)
   ============================================================ */
.interactive-exercise {
  background: var(--bg-card);
  border: var(--border-thin);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
}

.interactive-exercise h3 {
  font-family: var(--font-display);
  color: var(--color-primary);
  margin-bottom: var(--space-sm);
}

.interactive-exercise .exercise-description {
  color: var(--text-secondary);
  margin-bottom: var(--space-lg);
}

.interactive-exercise canvas {
  width: 100%;
  border-radius: var(--radius-md);
  border: var(--border-thin);
  background: var(--bg-card);
  cursor: pointer;
}

.interactive-exercise .exercise-controls {
  display: flex;
  gap: var(--space-md);
  margin-top: var(--space-md);
  flex-wrap: wrap;
  align-items: center;
}

.interactive-exercise .exercise-feedback {
  margin-top: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius-md);
  font-weight: 500;
  display: none;
}

.interactive-exercise .exercise-feedback.visible {
  display: block;
  animation: fadeIn var(--duration-normal) var(--ease-out);
}

.interactive-exercise .exercise-feedback.success {
  background: rgba(76, 175, 80, 0.08);
  border-left: 3px solid #4caf50;
  color: #2e7d32;
}

.interactive-exercise .exercise-feedback.error {
  background: rgba(232, 93, 74, 0.06);
  border-left: 3px solid var(--color-accent);
  color: var(--color-accent-dark);
}

/* Slider controls */
.exercise-slider {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  width: 100%;
}

.exercise-slider input[type="range"] {
  flex: 1;
  accent-color: var(--color-accent);
  height: 6px;
}

.exercise-slider .slider-value {
  font-family: var(--font-mono);
  font-size: var(--fs-small);
  color: var(--color-primary);
  min-width: 60px;
  text-align: center;
}

/* ============================================================
   CASE INPUT (improved textarea)
   ============================================================ */
.case-input {
  width: 100%;
  min-height: 100px;
  padding: var(--space-md) var(--space-lg);
  border: 2px solid var(--color-gray-light);
  border-radius: var(--radius-md);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: 1.7;
  resize: vertical;
  transition: border-color var(--duration-fast);
  background: var(--bg-warm);
  color: var(--text-primary);
  margin-bottom: var(--space-md);
}

.case-input:focus {
  border-color: var(--color-accent);
  outline: none;
}

/* ============================================================
   RESPONSIVE ADJUSTMENTS FOR NEW COMPONENTS
   ============================================================ */
@media (max-width: 768px) {
  .clinical-case { padding: var(--space-lg); }
  .quiz-multi .quiz-item { padding: var(--space-md); }
  .interactive-exercise { padding: var(--space-lg); }
}