body {
  display: flex;
  justify-content: center;
  background-color: rgb(221,221,221);
}

#content {
  position:absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
}

.bounce {
  width: 23px;
  height: 23px;
  border-radius: 50%;
  background-color: #6287a4;

  animation: bounce 1.25s;
  animation-direction: alternate;
  animation-timing-function: cubic-bezier(.5,0.05,1,.5);
  animation-iteration-count: infinite;
}

@keyframes bounce {
  from { transform: translate3d(0, 0, 0);     }
  to   { transform: translate3d(0, calc(100vh - 400px), 0); }
}