<style>
@keyframes test {
  from { transform: rotate3d(0, 0, 1, 90deg); }
  to { transform: rotate3d(0, 0, 1, -90deg); }
}
#target {
  animation: test 2s -1s paused;
  width: 100px;
  height: 100px;
  border: solid;
}
</style>
<div id="target"></div>