CSS only Combo Box with Checkboxes

Preview

HTML

<div class="combo-box">Select all that apply &#9660;
  <div class="combo-box-options"> 
    <label>Standard</label><br/>
    <input type='checkbox'/>
    <label>CSS</label><br/>
    <input type='checkbox'/>
    <label>HTML</label><br/>
    <input type='checkbox'/>
    <label>JavaScript</label><br/>    
    <hr/>
    <label>Other</label><br/>
    <input type='checkbox'/>
    <label>LESS</label><br/>
    <input type='checkbox'/>
    <label>Jade</label><br/>
    <input type='checkbox'/>
    <label>AngularJS</label><br/>
  </div> 
</div>

CSS

* {
  -webkit-box-sizing: border-box; 
  -moz-box-sizing: border-box;   
  box-sizing: border-box;   
}
.combo-box {
  float: left;
  z-index: 1;
  margin-left: 15px;
  margin-top: 15px;
  cursor: pointer;
  border: 1px solid black;
  width: 160px;
  padding: 5px;
}
.combo-box-options {
  display: none;
}
.combo-box:hover > .combo-box-options {
  z-index: 2;
  position: relative;
  display: block;
  margin-top: 6px;
  padding: 3px;
  margin-left: -6px;
  position: absolute;
  width: 160px;
  border-left: 1px solid black;
  border-right: 1px solid black;
  border-bottom: 1px solid black;
}

Source