body {
  margin: 0;
  padding: 0;
  background: #ee5253;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

.loader {
  width: 150px;
  height: 150px;
  position: relative;
}

span {
  position: absolute;
  width: 50px;
  height: 50px;
  background-color: white;
  border-radius: 4px;
  animation: chase 2s linear infinite;
}

span:nth-child(2) {
  animation-delay: 0.7s;
}

span:nth-child(3) {
  animation-delay: 01.4s;
}

@keyframes chase {
  0% {
    top: 0;
    left: 0;
  }

  12.5% {
    top: 0;
    left: 50%;
  }

  25% {
    top: 0;
    left: 50%;
  }

  37.5% {
    top: 50%;
    left: 50%;
  }

  50% {
    top: 50%;
    left: 50%;
  }

  62.5% {
    top: 50%;
    left: 0;
  }

  75% {
    top: 50%;
    left: 0;
  }

  87.5% {
    top: 0;
    left: 0;
  }

  100% {
    top: 0;
    left: 0;
  }
}