* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  min-height: 100vh;
  background: #111;
  overflow: hidden;
}

span{
  position: absolute;
  background: #f00;
  width: 10px;
  height: 10px;
  pointer-events: none;
  border-radius: 50%;
}

span::before{
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;
  background: #fff;
  border-radius: 50%;
  animation: moveParticles 2s linear infinite;
}

@keyframes moveParticles{
  0%{
    transform: translate(0);
  }
  100%{
    transform: translate(300px);
  }
}