@keyframes animate-x {
  from { transform: translateX(0); } to { transform: translateX(100%); }
}

@keyframes animate-y {
  from { transform: translateY(0); } to { transform: translateY(100%); }
}

.element {
  width: 200px;
  height: 200px;
  background-color: blue;
  transform-origin: center;
  animation:
    animate-x 20s linear infinite alternate,
    animate-y 15s linear infinite alternate;
}