.wrapper {
  --speed: 6s;
  --play-state: running;

  max-width: 900px;
  margin: 0 auto;
  padding: 40px 20px;
  text-align: center;
  font-family: Arial, sans-serif;
}

body {
  margin: 0;
  background: #e5e7eb;
}

.title {
  margin: 0 0 20px;
}

/* hide radios */
input[type="radio"] {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

/* traffic light */
.traffic-light {
  width: 70px;
  background: #111;
  padding: 12px;
  border-radius: 14px;
  margin: 0 auto 30px;
}

.light {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  margin: 10px auto;
  display: block;
  cursor: pointer;
  opacity: 0.25;
  transition: opacity 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
}

.red {
  background: #ef4444;
}

.yellow {
  background: #facc15;
}

.green {
  background: #22c55e;
}

/* active lights */
#stop:checked ~ .traffic-light .red {
  opacity: 1;
  box-shadow: 0 0 18px #ef4444;
}

#slow:checked ~ .traffic-light .yellow {
  opacity: 1;
  box-shadow: 0 0 18px #facc15;
}

#go:checked ~ .traffic-light .green {
  opacity: 1;
  box-shadow: 0 0 18px #22c55e;
}

/* variable changes */
#stop:checked ~ .road {
  --play-state: paused;
  --speed: 6s;
}

#slow:checked ~ .road {
  --play-state: running;
  --speed: 12s;
}

#go:checked ~ .road {
  --play-state: running;
  --speed: 2.5s;
}

/* road */
.road {
  position: relative;
  height: 160px;
  background: #374151;
  border-radius: 12px;
  overflow: hidden;
}

.road::before,
.road::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  height: 2px;
  background: repeating-linear-gradient(
    to right,
    transparent 0 20px,
    #f3f4f6 20px 40px
  );
}

.road::before {
  top: 53px;
}

.road::after {
  top: 106px;
}

/* cars */
.car {
  position: absolute;
  left: -90px;
  width: 70px;
  height: 32px;
  border-radius: 8px;
  animation-name: drive;
  animation-duration: var(--speed);
  animation-timing-function: linear;
  animation-iteration-count: infinite;
  animation-play-state: var(--play-state);
}

.car::before,
.car::after {
  content: "";
  position: absolute;
  bottom: -6px;
  width: 12px;
  height: 12px;
  background: #111;
  border-radius: 50%;
}

.car::before {
  left: 10px;
}

.car::after {
  right: 10px;
}

.car1 {
  top: 15px;
  background: #ef4444;
}

.car2 {
  top: 68px;
  background: #3b82f6;
  animation-delay: 1s;
}

.car3 {
  top: 121px;
  background: #22c55e;
  animation-delay: 2s;
}

@keyframes drive {
  from {
    left: -90px;
  }
  to {
    left: calc(100% + 20px);
  }
}