body {
  background: black;
}

img, div {
  width: 128px;
  height: 105px;
}

.x {
  -webkit-animation: x 13s linear infinite alternate;
          animation: x 13s linear infinite alternate;
}

.y {
  -webkit-animation: y 7s linear infinite alternate;
          animation: y 7s linear infinite alternate;
}

@-webkit-keyframes x {
  100% {
    transform: translateX(calc(100vw - 128px));
  }
}

@keyframes x {
  100% {
    transform: translateX(calc(100vw - 128px));
  }
}
@-webkit-keyframes y {
  100% {
    transform: translateY(calc(100vh - 105px));
  }
}
@keyframes y {
  100% {
    transform: translateY(calc(100vh - 105px));
  }
}