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<style type='text/css'>
  @keyframes hvr-wobble-vertical {
    16.65% { transform: translateY(8px); }
    33.3% { transform: translateY(-6px); }
    49.95% { transform: translateY(4px); }
    66.6% { transform: translateY(-2px); }
    83.25% { transform: translateY(1px); }
    100% { transform: translateY(0); }
  }

  .wp-to-top:active,
  .wp-to-top:focus,
  .wp-to-top:hover {
    animation-name: hvr-wobble-vertical;
    animation-duration: 1s;
    animation-timing-function: ease-in-out;
    animation-iteration-count: 1;
  }

  .wp-to-top {
    display: inline-block;
    position: fixed;
    bottom: 40px;
    left: 10px;
    padding: 10px;
    background: #000;
    color: #fff;
    z-index: 999;
  }
</style>

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