body {
  background: #222;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.traffic-light {
  background: #333;
  padding: 20px;
  border-radius: 30px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  align-items: center;
  box-shadow: 0 0 30px rgba(0,0,0,0.5);
}

.light {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: #111;
  box-shadow: inset 0 0 20px rgba(0,0,0,0.8);
  transition: background 0.5s, box-shadow 0.5s;
}

/* Active colors */
.red.active {
  background: red;
  box-shadow: 0 0 40px red;
}

.yellow.active {
  background: yellow;
  box-shadow: 0 0 40px yellow;
}

.green.active {
  background: limegreen;
  box-shadow: 0 0 40px limegreen;
}