/* ===== Base ===== */
* { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --azul: #2563eb;
  --azul-osc: #1e40af;
  --verde: #16a34a;
  --rojo: #dc2626;
  --gris-bg: #f1f5f9;
  --gris-card: #ffffff;
  --gris-borde: #e2e8f0;
  --texto: #1e293b;
  --texto-suave: #64748b;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--gris-bg);
  color: var(--texto);
  line-height: 1.6;
}

/* ===== Header ===== */
.app-header {
  background: linear-gradient(135deg, var(--azul), var(--azul-osc));
  color: #fff;
  padding: 1.5rem 1rem;
  text-align: center;
}
.app-header h1 { font-size: 1.6rem; }
.subtitle { opacity: 0.9; font-size: 0.95rem; margin-top: 0.25rem; }

/* ===== Contenedor ===== */
.container {
  max-width: 860px;
  margin: 1.25rem auto;
  padding: 0 1rem;
}

/* ===== Barra de tema ===== */
.tema-bar {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--gris-card);
  border: 1px solid var(--gris-borde);
  border-radius: 12px;
  padding: 0.75rem 1rem;
  margin-bottom: 1rem;
  flex-wrap: wrap;
}
.tema-bar label { font-weight: 600; white-space: nowrap; }
.tema-bar select {
  flex: 1;
  min-width: 160px;
  padding: 0.5rem;
  border: 1px solid var(--gris-borde);
  border-radius: 8px;
  font-size: 0.9rem;
  background: #fff;
}
.tema-bar select:disabled { opacity: 0.55; cursor: not-allowed; }
.badge {
  background: #fef3c7;
  color: #92400e;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
}

/* ===== Tabs ===== */
.tabs {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
  margin-bottom: 1rem;
}
.tab {
  flex: 1;
  min-width: 120px;
  padding: 0.7rem 0.5rem;
  border: 1px solid var(--gris-borde);
  background: var(--gris-card);
  border-radius: 10px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--texto-suave);
  transition: all 0.15s;
}
.tab:hover { background: #e0e7ff; }
.tab.active {
  background: var(--azul);
  color: #fff;
  border-color: var(--azul);
}

/* ===== Paneles ===== */
.panel {
  display: none;
  background: var(--gris-card);
  border: 1px solid var(--gris-borde);
  border-radius: 12px;
  padding: 1.5rem;
  animation: fade 0.2s ease;
}
.panel.active { display: block; }
.panel h2 { color: var(--azul-osc); margin-bottom: 1rem; }
.panel p { margin-bottom: 0.9rem; }
@keyframes fade { from { opacity: 0; } to { opacity: 1; } }

/* ===== Cards de puntos clave ===== */
.card {
  background: #f8fafc;
  border-left: 4px solid var(--azul);
  border-radius: 8px;
  padding: 1rem 1.2rem;
  margin-bottom: 1rem;
}
.card h3 { color: var(--azul-osc); margin-bottom: 0.5rem; font-size: 1.05rem; }
.card ul { padding-left: 1.2rem; }
.card li { margin-bottom: 0.35rem; }

.hint { color: var(--texto-suave); font-size: 0.9rem; margin-bottom: 1rem; }

/* ===== Flashcards ===== */
.flashcard-area { text-align: center; }
.flashcard {
  perspective: 1000px;
  width: 100%;
  max-width: 480px;
  height: 220px;
  margin: 0 auto 1rem;
  cursor: pointer;
}
.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 0.5s;
  transform-style: preserve-3d;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  font-size: 1.1rem;
  text-align: center;
}
.flashcard-front {
  background: linear-gradient(135deg, #dbeafe, #bfdbfe);
  color: var(--azul-osc);
  font-weight: 600;
  border: 2px solid #93c5fd;
}
.flashcard-back {
  background: linear-gradient(135deg, #dcfce7, #bbf7d0);
  color: #14532d;
  transform: rotateY(180deg);
  border: 2px solid #86efac;
}
.flashcard-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
}
.fc-counter { font-weight: 600; color: var(--texto-suave); min-width: 56px; }

/* ===== Botones ===== */
.btn {
  padding: 0.55rem 1.1rem;
  border: 1px solid var(--gris-borde);
  background: var(--gris-card);
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 600;
  transition: all 0.15s;
}
.btn:hover { background: #e0e7ff; }
.btn-primary {
  background: var(--verde);
  color: #fff;
  border-color: var(--verde);
}
.btn-primary:hover { background: #15803d; }

/* ===== Quiz ===== */
.pregunta {
  border: 1px solid var(--gris-borde);
  border-radius: 10px;
  padding: 1rem 1.2rem;
  margin-bottom: 1rem;
}
.pregunta-texto { font-weight: 600; margin-bottom: 0.7rem; }
.opcion {
  display: block;
  padding: 0.5rem 0.7rem;
  border-radius: 8px;
  cursor: pointer;
  margin-bottom: 0.35rem;
  transition: background 0.15s;
}
.opcion:hover { background: #f1f5f9; }
.opcion input { margin-right: 0.5rem; }
.opcion.correcta { background: #dcfce7; border: 1px solid var(--verde); }
.opcion.incorrecta { background: #fee2e2; border: 1px solid var(--rojo); }

.quiz-actions { display: flex; gap: 0.6rem; margin-top: 0.5rem; }
.quiz-result {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 10px;
  background: #eff6ff;
  border: 1px solid #bfdbfe;
  font-size: 1.1rem;
  font-weight: 600;
  text-align: center;
}

/* ===== Footer ===== */
.app-footer {
  text-align: center;
  color: var(--texto-suave);
  font-size: 0.85rem;
  padding: 1.5rem 1rem;
}

/* ===== Responsive ===== */
@media (max-width: 560px) {
  .tab { min-width: calc(50% - 0.2rem); }
  .flashcard { height: 200px; }
}