:root {
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  
  /* Paleta Dark Mode (Default) */
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #1e293b;
  --bg-card-hover: #334155;
  --bg-elevated: #273549;
  
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-faint: #64748b;
  
  --border-color: #334155;
  --border-light: #475569;
  
  --accent-blue: #38bdf8;
  --accent-cyan: #06b6d4;
  --accent-indigo: #818cf8;
  --accent-amber: #f59e0b;
  --accent-emerald: #10b981;
  --accent-rose: #f43f5e;
  
  --primary-gradient: linear-gradient(135deg, #0284c7 0%, #0369a1 50%, #4338ca 100%);
  --accent-gradient: linear-gradient(135deg, #38bdf8 0%, #818cf8 100%);
  --success-bg: rgba(16, 185, 129, 0.15);
  --success-border: #10b981;
  --error-bg: rgba(244, 63, 94, 0.15);
  --error-border: #f43f5e;
  
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.15);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.25), 0 2px 4px -2px rgb(0 0 0 / 0.2);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.35), 0 4px 6px -4px rgb(0 0 0 / 0.25);
  --shadow-glow: 0 0 25px rgba(56, 189, 248, 0.25);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-full: 9999px;
  
  --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Light Mode Overrides */
[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-card: #ffffff;
  --bg-card-hover: #f8fafc;
  --bg-elevated: #ffffff;
  
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-faint: #94a3b8;
  
  --border-color: #e2e8f0;
  --border-light: #cbd5e1;
  
  --accent-blue: #0284c7;
  --accent-cyan: #0891b2;
  --accent-indigo: #6366f1;
  
  --shadow-sm: 0 1px 3px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.08);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
  --shadow-glow: 0 0 20px rgba(2, 132, 199, 0.15);
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* Contenedor Principal */
.app-container {
  width: 100%;
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 1.25rem 3rem 1.25rem;
  flex: 1;
}

/* HEADER */
.main-header {
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(12px);
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: 1240px;
  margin: 0 auto;
  padding: 0.85rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand-wrapper {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand-icon {
  width: 44px;
  height: 44px;
  background: var(--primary-gradient);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
  font-size: 1.4rem;
  box-shadow: var(--shadow-glow);
}

.brand-title {
  font-size: 1.25rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1.2;
}

.brand-subtitle {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

.header-controls {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle-btn {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.5rem 0.85rem;
  border-radius: var(--radius-full);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  font-weight: 600;
  transition: var(--transition);
}

.theme-toggle-btn:hover {
  border-color: var(--accent-blue);
  background: var(--bg-card-hover);
}

/* NAVBAR TABS */
.nav-tabs {
  display: flex;
  gap: 0.5rem;
  background: var(--bg-secondary);
  padding: 0.4rem;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  margin: 1.5rem 0;
  overflow-x: auto;
}

.nav-tab-btn {
  flex: 1;
  min-width: 140px;
  padding: 0.75rem 1rem;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  transition: var(--transition);
  white-space: nowrap;
}

.nav-tab-btn:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.05);
}

.nav-tab-btn.active {
  background: var(--bg-card);
  color: var(--accent-blue);
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-color);
}

/* BANNER DE BIENVENIDA / TARGET INFO */
.target-alert-banner {
  background: linear-gradient(90deg, rgba(56, 189, 248, 0.12) 0%, rgba(129, 140, 248, 0.12) 100%);
  border: 1px solid rgba(56, 189, 248, 0.3);
  border-radius: var(--radius-lg);
  padding: 1.15rem 1.4rem;
  margin-bottom: 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.target-info {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.target-badge {
  background: var(--accent-blue);
  color: #0f172a;
  font-weight: 800;
  font-size: 0.75rem;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  white-space: nowrap;
}

.target-text {
  font-size: 0.92rem;
  color: var(--text-main);
}

.target-text strong {
  color: var(--accent-blue);
}

.quick-action-btn {
  background: var(--primary-gradient);
  color: #ffffff;
  border: none;
  padding: 0.55rem 1.25rem;
  border-radius: var(--radius-md);
  font-weight: 700;
  font-size: 0.88rem;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: var(--shadow-sm);
}

.quick-action-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

/* SECCIONES PRINCIPALES */
.app-section {
  display: none;
  animation: fadeIn 0.3s ease forwards;
}

.app-section.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* =======================================================
   MODO ESTUDIO
======================================================= */
.study-layout {
  display: grid;
  grid-template-columns: 290px 1fr;
  gap: 1.75rem;
}

@media (max-width: 900px) {
  .study-layout {
    grid-template-columns: 1fr;
  }
}

.study-sidebar {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  box-shadow: var(--shadow-sm);
  height: fit-content;
}

.sidebar-title {
  font-size: 0.95rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.unit-selector-list {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.unit-nav-item {
  background: transparent;
  border: 1px solid transparent;
  padding: 0.75rem 0.95rem;
  border-radius: var(--radius-md);
  color: var(--text-main);
  text-align: left;
  cursor: pointer;
  font-family: inherit;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  transition: var(--transition);
}

.unit-nav-item:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-color);
}

.unit-nav-item.active {
  background: rgba(56, 189, 248, 0.1);
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.unit-nav-item.priority {
  position: relative;
}

.priority-tag {
  font-size: 0.65rem;
  background: var(--accent-amber);
  color: #0f172a;
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-full);
  font-weight: 800;
  align-self: flex-start;
  margin-bottom: 0.15rem;
}

.unit-nav-title {
  font-weight: 700;
  font-size: 0.9rem;
  line-height: 1.3;
}

.unit-nav-sub {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Área de Contenido de Estudio */
.study-content-area {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
}

.study-header {
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1.25rem;
  margin-bottom: 1.75rem;
}

.study-unit-tag {
  color: var(--accent-blue);
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.35rem;
}

.study-unit-title {
  font-size: 1.65rem;
  font-weight: 800;
  color: var(--text-main);
  line-height: 1.25;
}

.study-unit-desc {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-top: 0.5rem;
}

.study-topic-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  margin-bottom: 1.5rem;
  overflow: hidden;
  transition: var(--transition);
}

.study-topic-card:hover {
  border-color: var(--border-light);
}

.topic-card-header {
  padding: 1.15rem 1.4rem;
  background: rgba(255, 255, 255, 0.02);
  border-bottom: 1px solid var(--border-color);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.topic-card-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.topic-toggle-icon {
  font-size: 0.85rem;
  color: var(--text-muted);
  transition: transform 0.25s ease;
}

.study-topic-card.collapsed .topic-toggle-icon {
  transform: rotate(-90deg);
}

.study-topic-card.collapsed .topic-card-body {
  display: none;
}

.topic-card-body {
  padding: 1.5rem;
}

.topic-card-body h4 {
  font-size: 1rem;
  color: var(--accent-blue);
  margin: 1.25rem 0 0.5rem 0;
}

.topic-card-body h4:first-child {
  margin-top: 0;
}

.topic-card-body p {
  color: var(--text-main);
  margin-bottom: 0.85rem;
  font-size: 0.94rem;
}

.topic-card-body ul, .topic-card-body ol {
  margin-left: 1.4rem;
  margin-bottom: 1rem;
  color: var(--text-main);
  font-size: 0.94rem;
}

.topic-card-body li {
  margin-bottom: 0.4rem;
}

/* Cajas de Fórmulas y Notas */
.formula-box {
  background: var(--bg-elevated);
  border-left: 4px solid var(--accent-blue);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin: 1rem 0;
}

.formula-box code {
  font-family: 'Consolas', 'Courier New', monospace;
  font-size: 1.05rem;
  color: #38bdf8;
  font-weight: 700;
  display: block;
  margin-bottom: 0.35rem;
}

.formula-box p {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 0;
}

.note-box {
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.3);
  padding: 0.9rem 1.15rem;
  border-radius: var(--radius-md);
  color: var(--text-main);
  font-size: 0.9rem;
  margin: 1rem 0;
}

.table-custom {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 1.5rem 0;
  font-size: 0.88rem;
}

.table-custom th, .table-custom td {
  padding: 0.75rem 0.9rem;
  border: 1px solid var(--border-color);
  text-align: left;
}

.table-custom th {
  background: var(--bg-elevated);
  color: var(--accent-blue);
  font-weight: 700;
}

.table-custom tr:nth-child(even) {
  background: rgba(255, 255, 255, 0.02);
}

.power-triangle-diagram {
  background: var(--bg-elevated);
  border: 1px dashed var(--accent-blue);
  padding: 1rem;
  border-radius: var(--radius-md);
  margin: 1rem 0;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  font-size: 0.9rem;
}

/* =======================================================
   MODO EXAMEN
======================================================= */
.exam-container {
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
}

.exam-setup-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
}

.setup-header {
  margin-bottom: 1.5rem;
}

.setup-title {
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--text-main);
}

.setup-subtitle {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-top: 0.25rem;
}

/* Presets rápidos */
.presets-section {
  margin-bottom: 1.5rem;
}

.presets-label {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin-bottom: 0.65rem;
}

.presets-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 0.75rem;
}

.preset-btn {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.85rem 1rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  text-align: left;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.preset-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-blue);
}

.preset-btn.featured {
  background: rgba(56, 189, 248, 0.12);
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.preset-btn.featured:hover {
  background: rgba(56, 189, 248, 0.2);
}

.preset-sub {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 400;
}

/* Unidades Checkbox Selection */
.units-selection-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  margin-bottom: 1.5rem;
}

.units-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 0.85rem;
  margin-top: 0.85rem;
}

.unit-checkbox-label {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 0.85rem 1rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
}

.unit-checkbox-label:hover {
  border-color: var(--accent-blue);
}

.unit-checkbox-label input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent-blue);
  margin-top: 0.2rem;
  cursor: pointer;
}

.unit-chk-info {
  display: flex;
  flex-direction: column;
}

.unit-chk-name {
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--text-main);
}

.unit-chk-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Opciones de examen (preguntas y modo) */
.exam-params-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.25rem;
  margin-bottom: 1.75rem;
}

.param-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.param-group label {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.param-select {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.75rem 1rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  outline: none;
  transition: var(--transition);
}

.param-select:focus {
  border-color: var(--accent-blue);
  box-shadow: 0 0 0 2px rgba(56, 189, 248, 0.2);
}

/* Botón Iniciar Examen */
.start-exam-action {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  padding-top: 1rem;
  border-top: 1px solid var(--border-color);
}

.questions-available-count {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.questions-available-count strong {
  color: var(--accent-blue);
}

.btn-start-exam {
  background: var(--primary-gradient);
  color: #ffffff;
  border: none;
  padding: 0.9rem 2.25rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 1.05rem;
  font-weight: 800;
  cursor: pointer;
  box-shadow: var(--shadow-md);
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.btn-start-exam:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

/* =======================================================
   PANTALLA DE PREGUNTA ACTIVA
======================================================= */
.active-quiz-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-md);
  display: none;
}

.quiz-top-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.quiz-meta-info {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.quiz-question-counter {
  font-weight: 800;
  font-size: 1rem;
  color: var(--text-main);
}

.quiz-unit-badge {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--accent-blue);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
}

.quiz-timer-box {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--accent-amber);
  background: rgba(245, 158, 11, 0.1);
  padding: 0.35rem 0.85rem;
  border-radius: var(--radius-full);
}

/* Barra de progreso */
.quiz-progress-bar-container {
  width: 100%;
  height: 8px;
  background: var(--bg-secondary);
  border-radius: var(--radius-full);
  margin-bottom: 2rem;
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  width: 0%;
  background: var(--primary-gradient);
  border-radius: var(--radius-full);
  transition: width 0.3s ease;
}

/* Enunciado */
.question-prompt {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.4;
  margin-bottom: 1.75rem;
}

/* Opciones de respuesta */
.options-grid {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
  margin-bottom: 1.75rem;
}

.option-btn {
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  color: var(--text-main);
  padding: 1.1rem 1.35rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.98rem;
  font-weight: 500;
  text-align: left;
  line-height: 1.4;
  transition: var(--transition);
  display: flex;
  align-items: flex-start;
  gap: 1rem;
}

.option-letter {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  width: 28px;
  height: 28px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.82rem;
  font-weight: 800;
  flex-shrink: 0;
  transition: var(--transition);
}

.option-btn:hover:not(:disabled) {
  background: var(--bg-card-hover);
  border-color: var(--accent-blue);
}

.option-btn:hover:not(:disabled) .option-letter {
  background: var(--accent-blue);
  color: #0f172a;
}

/* Estados de feedback */
.option-btn.selected {
  border-color: var(--accent-blue);
  background: rgba(56, 189, 248, 0.1);
}

.option-btn.correct {
  background: var(--success-bg) !important;
  border-color: var(--success-border) !important;
  color: #10b981;
}

.option-btn.correct .option-letter {
  background: #10b981;
  color: #ffffff;
}

.option-btn.incorrect {
  background: var(--error-bg) !important;
  border-color: var(--error-border) !important;
  color: #f43f5e;
}

.option-btn.incorrect .option-letter {
  background: #f43f5e;
  color: #ffffff;
}

/* Explicación tras responder */
.quiz-explanation-box {
  background: var(--bg-secondary);
  border-left: 4px solid var(--accent-cyan);
  padding: 1.25rem;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin-bottom: 1.75rem;
  display: none;
  animation: fadeIn 0.3s ease;
}

.explanation-title {
  font-size: 0.95rem;
  font-weight: 800;
  color: var(--accent-cyan);
  margin-bottom: 0.4rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.explanation-text {
  font-size: 0.92rem;
  color: var(--text-main);
  line-height: 1.5;
}

/* Botones de acción del Quiz */
.quiz-footer-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.btn-secondary {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.btn-secondary:hover {
  background: var(--bg-card-hover);
  color: var(--text-main);
}

.btn-primary {
  background: var(--primary-gradient);
  color: #ffffff;
  border: none;
  padding: 0.85rem 1.75rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

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

/* =======================================================
   PANTALLA DE RESULTADOS
======================================================= */
.quiz-results-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2.5rem 2rem;
  box-shadow: var(--shadow-lg);
  display: none;
  text-align: center;
}

.results-badge-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto 1.25rem auto;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
}

.results-badge-icon.pass {
  background: rgba(16, 185, 129, 0.15);
  color: #10b981;
  border: 2px solid #10b981;
}

.results-badge-icon.fail {
  background: rgba(244, 63, 94, 0.15);
  color: #f43f5e;
  border: 2px solid #f43f5e;
}

.results-title {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.results-status-msg {
  color: var(--text-muted);
  font-size: 1rem;
  max-width: 600px;
  margin: 0 auto 2rem auto;
}

.results-score-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  max-width: 750px;
  margin: 0 auto 2.5rem auto;
}

.score-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 1.25rem;
  border-radius: var(--radius-md);
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.score-box-label {
  font-size: 0.78rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 700;
  letter-spacing: 0.05em;
}

.score-box-val {
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--accent-blue);
}

.results-breakdown-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  max-width: 800px;
  margin: 0 auto 2rem auto;
  text-align: left;
}

.breakdown-title {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: var(--text-main);
}

.results-actions-row {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

/* =======================================================
   FLASHCARDS (TARJETAS INTERACTIVAS)
======================================================= */
.flashcards-container {
  max-width: 700px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.flashcard-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.flashcard-wrapper {
  perspective: 1000px;
  width: 100%;
  min-height: 320px;
  cursor: pointer;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  min-height: 320px;
  text-align: center;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
}

.flashcard-wrapper.flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  border-radius: var(--radius-lg);
  padding: 2.5rem 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border-color);
}

.flashcard-front {
  background: var(--bg-card);
}

.flashcard-back {
  background: var(--bg-elevated);
  transform: rotateY(180deg);
  border-color: var(--accent-blue);
}

.fc-unit-tag {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent-blue);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
}

.fc-text {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.4;
  margin-bottom: 1.25rem;
}

.fc-answer {
  font-size: 1.05rem;
  color: var(--text-main);
  line-height: 1.5;
  white-space: pre-line;
}

.fc-hint {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: auto;
}

.flashcard-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* =======================================================
   CALCULADORAS INTERACTIVAS
======================================================= */
.calculators-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(360px, 1fr));
  gap: 1.75rem;
}

.calc-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.calc-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent-blue);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.calc-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.calc-inputs {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.calc-field {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.calc-field label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-main);
}

.calc-field input {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.65rem 0.85rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.95rem;
  outline: none;
  transition: var(--transition);
}

.calc-field input:focus {
  border-color: var(--accent-blue);
}

.calc-result-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.calc-res-item {
  display: flex;
  justify-content: space-between;
  font-size: 0.88rem;
}

.calc-res-item strong {
  color: var(--accent-blue);
}

/* FOOTER */
.main-footer {
  margin-top: auto;
  border-top: 1px solid var(--border-color);
  padding: 1.5rem 1.25rem;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* =======================================================
   BIBLIOTECA MULTIMEDIA (INFOGRAFÍAS Y PDFs)
======================================================= */
.media-tabs-nav {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.media-tab-btn {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: var(--transition);
}

.media-tab-btn:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-blue);
}

.media-tab-btn.active {
  background: rgba(56, 189, 248, 0.15);
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.infographics-container {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 1.5rem;
  align-items: start;
}

@media (max-width: 900px) {
  .infographics-container {
    grid-template-columns: 1fr;
  }
}

.infographics-list {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.info-card-selector {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.info-card-selector:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-blue);
}

.info-card-selector.active {
  border-color: var(--accent-blue);
  background: rgba(56, 189, 248, 0.1);
}

.info-card-title {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--text-main);
}

.info-card-desc {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.info-tags-row {
  display: flex;
  gap: 0.35rem;
  flex-wrap: wrap;
  margin-top: 0.3rem;
}

.info-tag-pill {
  font-size: 0.7rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--accent-blue);
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-full);
}

.infographic-display-area {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.info-display-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.info-display-title {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text-main);
}

.info-image-wrapper {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 0.5rem;
  cursor: zoom-in;
}

.info-image-wrapper img {
  max-width: 100%;
  max-height: 700px;
  object-fit: contain;
  border-radius: var(--radius-sm);
  transition: transform 0.3s ease;
}

.info-image-wrapper img:hover {
  transform: scale(1.015);
}

/* Grilla de PDFs */
.pdf-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
}

.pdf-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  transition: var(--transition);
}

.pdf-card:hover {
  border-color: var(--accent-blue);
  box-shadow: var(--shadow-md);
}

.pdf-header {
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
}

.pdf-icon-box {
  width: 48px;
  height: 48px;
  background: rgba(244, 63, 94, 0.15);
  border: 1px solid rgba(244, 63, 94, 0.3);
  color: #f43f5e;
  font-size: 1.5rem;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.pdf-title {
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-main);
  line-height: 1.3;
}

.pdf-badge {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent-blue);
  background: rgba(56, 189, 248, 0.1);
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-full);
  display: inline-block;
  margin-top: 0.25rem;
}

.pdf-desc {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.45;
  flex: 1;
}

.pdf-actions {
  display: flex;
  gap: 0.65rem;
  flex-wrap: wrap;
  padding-top: 0.75rem;
  border-top: 1px solid var(--border-color);
}

.btn-open-pdf {
  flex: 1;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.65rem 0.95rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 700;
  text-decoration: none;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  transition: var(--transition);
  cursor: pointer;
}

.btn-open-pdf:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent-blue);
  color: var(--accent-blue);
}

.btn-embed-pdf {
  background: var(--primary-gradient);
  color: #ffffff;
  border: none;
  padding: 0.65rem 1rem;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  transition: var(--transition);
}

.btn-embed-pdf:hover {
  box-shadow: var(--shadow-glow);
}

/* Modal Integrado de PDF / Imagen */
.media-modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(8px);
  z-index: 100;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
}

.media-modal-backdrop.active {
  display: flex;
  animation: fadeIn 0.25s ease;
}

.media-modal-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 1100px;
  height: 88vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.media-modal-header {
  padding: 1rem 1.4rem;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.media-modal-title {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.media-modal-close-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  width: 36px;
  height: 36px;
  border-radius: 50%;
  font-size: 1.1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.media-modal-close-btn:hover {
  background: var(--error-bg);
  color: var(--accent-rose);
  border-color: var(--accent-rose);
}

.media-modal-body {
  flex: 1;
  padding: 1rem;
  overflow: auto;
  display: flex;
  justify-content: center;
  align-items: center;
  background: var(--bg-primary);
}

.media-modal-body iframe {
  width: 100%;
  height: 100%;
  border: none;
  border-radius: var(--radius-md);
}

.media-modal-body img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
}

/* RESPONSIVE AJUSTES */
@media (max-width: 640px) {
  .header-inner {
    flex-direction: column;
    align-items: flex-start;
  }
  .header-controls {
    align-self: flex-end;
  }
  .nav-tabs {
    flex-wrap: nowrap;
    overflow-x: auto;
  }
  .quiz-footer-actions {
    flex-direction: column-reverse;
  }
  .btn-primary, .btn-secondary {
    width: 100%;
    justify-content: center;
  }
}