html,
body {
  width: 100%;
  height: 100%;
  position: relative;
  background-color: #383838;
}

.viewport {
  width: 100%;
  height: 100%;
  position: absolute;
  perspective: 600px;
  overflow: hidden;
}

.field {
  transform-origin: 50% 0;
  top: 50%;
  left: 50%;
  height: 400%;
  width: 1000%;
  position: absolute;
  transform: translateX(-50%) rotateX(85deg);
  background-image: linear-gradient(to right, transparent 50%, #dbd9da 50%, #dbd9da 100%, transparent 100%);
  background-size: 1% 100%;
  border-top: 30px solid #dbd9da;
  animation: panRight 30s linear infinite;
}

@keyframes panRight {
  0% {
    transform: translateX(-50%) rotateX(85deg);
  }
  100% {
    transform: translateX(-75%) rotateX(85deg);
  }
}