html {
  background-color: #000000;
  color: #00FF01;
  display: table;
  width: 100%;
  height: 100%;
  margin: 0;
}

body {
  display: table-cell;
  vertical-align: middle;
}

.center {
  margin: 0 auto;
}

.three-char-input {
  width: 4ch;
}

.five-char-input {
  width: 6ch;
}

.noselect {
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}