Selection of multiple Images in UI using Checkbox

Selection of multiple Images in UI using Checkbox

HTML:

<ul>
  <li><input type="checkbox" id="cb1" />
    <label for="cb1"><img src="http://lorempixel.com/100/100" /></label>
  </li>
  <li><input type="checkbox" id="cb2" />
    <label for="cb2"><img src="http://lorempixel.com/101/101" /></label>
  </li>
  <li><input type="checkbox" id="cb3" />
    <label for="cb3"><img src="http://lorempixel.com/102/102" /></label>
  </li>
  <li><input type="checkbox" id="cb4" />
    <label for="cb4"><img src="http://lorempixel.com/103/103" /></label>
  </li>
</ul>

CSS:

ul {
  list-style-type: none;
}

li {
  display: inline-block;
}

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

label {
  border: 1px solid #fff;
  padding: 10px;
  display: block;
  position: relative;
  margin: 10px;
  cursor: pointer;
}

label:before {
  background-color: white;
  color: white;
  content: " ";
  display: block;
  border-radius: 50%;
  border: 1px solid grey;
  position: absolute;
  top: -5px;
  left: -5px;
  width: 25px;
  height: 25px;
  text-align: center;
  line-height: 28px;
  transition-duration: 0.4s;
  transform: scale(0);
}

label img {
  height: 100px;
  width: 100px;
  transition-duration: 0.2s;
  transform-origin: 50% 50%;
}

:checked + label {
  border-color: #ddd;
}

:checked + label:before {
  content: "✓";
  background-color: grey;
  transform: scale(1);
}

:checked + label img {
  transform: scale(0.9);
  box-shadow: 0 0 5px #333;
  z-index: -1;