body {
  font: 1em Arial;
}

.square {
  width: 60px;
  height: 60px;
  background: #333;
  margin: 30px;
  box-shadow: 0 0 4px rgba(0, 0, 0, 0.4);
  animation: spin 2s linear 1s infinite alternate;
}

.square:hover {
  animation-play-state: paused;
}

@keyframes spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

.container {
  width: 200px;
  height: 30px;
  border: 3px solid #fff;
  background: #999;
  overflow: hidden;
  border-radius: 7px;
  margin: 40px;
  box-shadow: 0 3px 4px rgba(0, 0, 0, 0.3);
}

.bar {
  width: 400px;
  height: 30px;
  background: repeating-linear-gradient(
    45deg,
    rgba(255, 255, 255, 0.9),
    rgba(255, 255, 255, 0.9) 5px,
    transparent 5px,
    transparent 10px
  );
  animation: slide 3s linear infinite;
}

@keyframes slide {
  0% {
    margin-left: 0%;
  }
  50% {
      opacity: 0;
  }
  100% {
      margin-left: -100%;
  }
}