#traffic-light {
  height: 250px;
  width: 100px;
  background-color: #777;
  background: linear-gradient(90deg, rgb(171, 171, 171) 0%, rgb(129, 129, 129) 100%);
  border-radius: 20px;
  margin: 5px 0;
  padding: 20px;
}

.bulb {
  height: 60px;
  width: 60px;
  background: #444;
  border-radius: 50%;
  border: 2px solid #888;
  margin: 7px auto;
  transition: background 500ms;
}