* {
  box-sizing: border-box;
}

.flip.number-flip {
  display: inline-block;
  background: #333
}

.digit {
  color: #fff;
  font-size: 28px;
  padding: 10px 5px;
  text-align: center;
}

.flip .ctnr:last-of-type .digit {
  color: red
}

.slot .ctnr {
  background: #000;
  border: 1px solid #fff;
}