*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

main {
  min-height: 100vh;
  display: grid;
  place-items: center;
}

.traffic-light {
  display: grid;
  gap: 1rem;
}

.traffic-light .box {
  width: 8rem;
  height: 20rem;
  background-color: #1d1e22;
  border-radius: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
  justify-content: center;
  align-items: center;
}

.light {
  width: 5rem;
  aspect-ratio: 1 / 1;
  border-radius: 50%;
}

.red {
  background-color: #300;
}

.red.on {
  background-color: #f00;
}

.yellow {
  background-color: #330;
}

.yellow.on {
  background-color: #ff0;
}

.green {
  background-color: #030;
}

.green.on {
  background-color: #0f0;
}

.timer-box {
  background-color: #555;
  border: 5px solid #333;
  border-radius: 1rem;
  padding: 0.5rem 1rem;
  text-align: center;
}

#timer {
  font-family: "Courier New", Courier, monospace;
  font-weight: 700;
  font-size: 4rem;
}

#timer.go {
  color: #0f0;
}

#timer.wait {
  color: #ff0;
}

#timer.stop {
  color: #f00;
}