@keyframes swing { 
  20% { transform: rotate3d(0, 0, 1, 15deg); }
  40% { transform: rotate3d(0, 0, 1, -10deg); }
  60% { transform: rotate3d(0, 0, 1, 5deg); }
  80% { transform: rotate3d(0, 0, 1, -5deg); }
  100% { transform: rotate3d(0, 0, 1, 0deg); }
}
.swing { transform-origin: center top; animation-name: swing; }