body {
  font-family: Arial, Helvetica, sans-serif;
  background-color: #f1f1f1;
  display: flex;
  flex-direction: column;
  align-items: center;
  background-color: black;
  color: lightgrey;
}

#display-0 {
  border: 4px solid grey;
  border-radius: 4px;
  width: 100%;
}

form {
  padding: 16px;
  display: flex;
  flex-direction: column;
}

fieldset div, form div {
  display: flex;
  flex-direction: row;
  justify-content: space-between;
}

form div {
  padding: .1em;
}