* {
  box-sizing: border-box;
}
footer {
  border-top: solid 1px #777;
  padding: 1em 0;
  font-size: 80%;
  margin-top: 1em;
}

label {
  display: block;
  margin-bottom: 0.5em;
}

output {
  display: block;
}

.hidden {
  display: none;
}

output img {
  padding: 1em;
  max-width: 100%;
}