html {
  font-size: 1em;
  line-height: 1.5em;
  font-family: 'Verdana', Helvetica, sans-serif;
}

body {
  margin: 0;
  background: #f3f3f3;
}

.encabezado {
  text-align: center;
  background: #006699;
  border-bottom: 0.1em solid silver;  
  padding: 0.5em;
}

.footer-principal {
  text-align: center;
  background: #006699;
  border-bottom: 0.1em solid silver;  
  padding: 1em;
  }

.principal {
  max-width: 900px;
  margin: auto;
  padding: 1em;
}

.caja1 {
  background: #fff;
  border: 0.1em solid gray;
  padding: 1em;
  margin: 1em;
  box-shadow: 0 0 0.1em 0.01em black;
}

.caja1 h2 {
  font-family: 'Verdana', sans-serif;
  color: darkblue;
  text-shadow: 0.03em 0.03em 0.01em #000;
  letter-spacing: 0.03em;
}

.caja2 {
  background: #fff;
  border: 0.1em solid gray;
  padding: 1em;
  margin: 1em;
  box-shadow: 0 0 0.1em 0.01em black;
}

.caja2 h2 {
  font-family: 'Verdana', sans-serif;
  color: darkblue;
  text-shadow: 0.03em 0.03em 0.01em #000;
  letter-spacing: 0.03em;
}

.articulo {
  margin-top: 2em;
}

.solucion p.fira {
font-family: "Fira Sans";
font-size: 1.2em;
}

.solucion p.roboto {
font-family: 'Roboto', sans-serif;
font-size: 1em;
}