.cell {
  width: 60px;
  height: 60px;
  margin: 8px auto;
  border: 1px solid;
  border-radius: 50%;
}

.traffic-light {
  border: 1px solid;
  width: 90px;
  margin: 10px 0;
}

.red {
  background-color: red;
}

.yellow {
  background-color: yellow;
}

.green {
  background-color: green;
}