.rolling-ball {
  position: absolute;
  top: 50%;
  left: -200px;
  width: 100px; /* adjust as needed */
  animation: rollAcross 4s forwards;
  z-index: 9999;
}

@keyframes rollAcross {
  0% {
    left: -200px;
    opacity: 1;
  }
  90% {
    left: 100vw;
    opacity: 1;
  }
  100% {
    left: 100vw;
    opacity: 0;
    display: none;
  }
}