.progress-bar {
  position: relative;
}

.progress-bar__progress {
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  z-index: -1;
  background-color: lightgreen;
}

@keyframes moving-gradient {
  0% {
    background-position: left bottom;
  }
  100% {
    background-position: right bottom;
  }
}

.progress-bar__progress.animate {
  background-image: linear-gradient(
    90deg,
    transparent 25%,
    rgba(255, 255, 255, 0.25) 50%,
    transparent 75%
  );
  background-repeat: repeat;
  background-size: 50% 100%;

  animation-name: moving-gradient;
  animation-duration: 1.4s;
  animation-iteration-count: infinite;
  animation-timing-function: linear;
}