.illusion {
  background: linear-gradient(90deg, #595959, #fff);
  width: 150px;
  height: 150px;
  top: 50%;
  left: 50%;
  display: block;
  position: absolute;
  border-radius: 50%;
  animation: rotation 5s linear infinite;
}

.illusion:before {
  background: linear-gradient(270deg, #595959, #fff);
  width: 130px;
  height: 130px;
  top: 10px;
  right: 0;
  display: block;
  position: absolute;
  content: "";
  border-radius: 50%;
}

.illusion:after {
  background: #fff;
  width: 110px;
  height: 110px;
  top: 20px;
  left: 20px;
  display: block;
  position: absolute;
  content: "";
  border-radius: 50%;
}

@keyframes rotation {
  from {
    transform: translate(-50%, -50%) rotate(0deg);
  }
  to {
    transform: translate(-50%, -50%) rotate(360deg);
  }
}