body { 
  font-family: 'Segoe UI', sans-serif;
  margin: 0;
  padding: 0;
  background: linear-gradient(135deg, #81d4fa, #0288d1); /* celeste */
  color: #212121;
}

/* Encabezado */
header {
  background-color: #01589b; /* celeste bien oscuro */
  color: red;
  padding:
}