#myButton {
  padding: 50px;
  background: yellow;
  cursor: pointer;
  transition-property: background, transform;
  transition-duration: 1s,         0.5s;
  transition-delay:    0s,         1s;
  display: inline-block;
  transform: rotate(0deg);
}

#myButton:hover {
  background: cyan;
  transform: rotate(90deg);
}