html, body {
  height: 100%;
  padding: 0;
  margin: 0;
  font-family: 'Fira Sans', sans-serif;
}
header {
  width: 100%;
  position: fixed;
  top: 0;
  background-color: #747474;
  height: 10%;
}
  header h1 {
    margin: 0;
    padding-left: 5%;
    font-size: 5vh;
  }
  header h2 {
    margin: 0;
    padding-left: 5%;
    font-size: 3vh;
  }
section {
  position: relative;
  top: 10%;
}
  section h1 {
    margin-left: 10%;
  }

  section article {
    margin-left: 10%;
  }
  section article h1 {
    font-size: 4vh;
  }
  section article h2 {
    font-size: 3vh;
  }
  section article p {
    font-size: 2.5vh;
    color: #0f2f3c
  }

  section .pantalla .respuesta {
    background-color: #000000;
    vertical-align: middle;
    width: 250px;
    height: 40px;
    color: #ffffff;
    margin: 0;
    padding: 0;
  }

  section .pantalla #campo1 {
    margin: 20px 0;
    vertical-align: middle;
    height: 40px;
    width: 250px;
  }

  section article .botonera button {
    background-color: #747474;
    border: none;
    color: #ffffff;
    width: 90px;
    height: 40px;
    text-align: center;
    text-decoration: none;
    font-size: 100%;
    font-weight:bold;
    display: inline-block;
    margin: 0;
    padding: 0;
  }
  section article .botonera button:hover {
    background-color: #ffffff;
    color: #000000;
  }
  section article .botonera button sup {
    font-size: 0.83em;
    vertical-align: super;
    line-height: 0;
  }
footer {
  width: 100%;
  position: fixed;
  bottom: 0;
  height: 10%;
  /*display: block;*/
  background-color: #747474;
}
  footer p {
    padding-left: 5%;
    vertical-align: middle;
  }