Add CSS animations to checkbox label

HTML

<input type="checkbox" id="pizza" name="food" />
<label for="pizza">Pizza</label>

CSS

input[type="checkbox"] {
  display: none;
}

label {
  padding-left: 20px;
}

label::before {
  content: "";
  display: inline-block;
  width: 20px;
  height: 20px;
  vertical-align: middle;
  margin-left: -10px;
  margin-right: 10px;
  transition: .5s;
  background-image: url(data:image/svg+xml;utf8;base64,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);
  background-size: 100%;
  transform: none;
  opacity: 0;
  animation:...