<div class="checkbox">
  <input type="checkbox" id="checkbox">
  <label for="checkbox"></label>
</div>
.checkbox {
  width: 40px;
  height: 40px;
  border: 2px solid black;
  border-radius: 50%;
}

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

.checkbox label {
  display: block;
  width: 20px;
  height: 20px;
  margin: 10px;
  background-color: black;
  border-radius: 50%;
  opacity: 0;
/*   filter: alpha(opacity=0); */
}

.checkbox input[type=checkbox]:checked + label {
  opacity: 1;
/*   filter: alpha(opacity=1); */
}

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