input,button,#error {
   font-size: 7vw;
}

body {
  display: grid;
  justify-content: center;
  align-content: center;
}

#pane {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  flex-direction: column;
  align-content: stretch;
  row-gap: 0.4em;
  padding: 2em;
  background: lightgray;
  border-radius: 6px;
}

.digits {
  display: flex;
  flex-wrap: wrap;
  column-gap: 0.2em;
}

.digit {
}

.invalid {
  background: hsl(1deg 100% 91%);
}

#error {
  display: none;
}