<div class="box"></div>

body {
  height: 100vh;
  background-image: linear-gradient(to top, greenyellow, skyblue);
}

.box {
  width: 50px;
  height: 50px;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  margin: auto;
}

.box::before {
  content: '';
  width: 50px;
  height: 5px;
  background: #000;
  position: absolute;
  top: 58px;
  left: 0;
  border-radius: 50%;
  opacity: 0.2;
  animation: shadow 0.6s linear infinite;
}

@keyframes shadow {
  0% {
    transform: scale(1, 1);
  }
  50% {
    transform: scale(1.2, 1);
  }
  100% {
    transform: scale(1, 1);
  }
}

.box::after {
  content: '';
  background: yellow;
  width: 50px;
  height: 50px;
  position: absolute;
  left: 0;
  top: 0;
  border-radius: 3px;
  animation: load 0.6s linear infinite;
}

@keyframes load {
  17% {
    border-bottom-right-radius: 3px;
  }
  25% {
    transform: translatey(9px) rotate(22.5deg);
  }
  50% {
    transform: translatey(18px) scale(1, 0.9) rotate(45deg);
    border-bottom-right-radius: 40px;
  }
  75% {
    transform: translatey(9px) rotate(67.5deg);
  }
  100% {
    transform: translatey(0px) rotate(90deg); 
  }
}