.runner {
  position: fixed;
  bottom: 20px;
  left: -200px;
  width: 120px;
  z-index: 10000;
  pointer-events: none;
  opacity: 0;
}

.runner.active {
  animation: runAcross 4s linear forwards;
  opacity: 1;
}

@keyframes runAcross {
  0% {
    left: -200px;
  }
  100% {
    left: 110%;
  }
}