选中和取消选中时的自定义复选框动画: CSS

<label class="checkbox-container">
  <input type="checkbox">
  <span class="checkmark"></span>
  Checkbox
</label>

.checkbox-container {
  position: relative;
  padding-left: 35px;
  cursor: pointer;
}

.checkbox-container input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
}

.checkmark {
  position: absolute;
  top: 0;
  left: 0;
  height: 25px;
  width: 25px;
  background-color: #eee;
}

.checkbox-container:hover .checkmark {
  background-color: #ccc;
}

.checkbox-container input:checked ~ .checkmark {
  background-color: #2196F3;
}

.checkmark:after {
  content: "";
  position: absolute;
  display: none;
}

.checkbox-container input:checked ~ .checkmark:after {
  display: block;
}

.checkbox-container .checkmark:after {
  left: 9px;
  top: 5px;
  width: 5px;
  height: 10px;
  border: solid white;
  border-width: 0 3px 3px 0;
  transform: rotate(45deg);
}