Custom checkbox using only CSS and HTML
<p>I need to create a custom checkbox using only html and CSS. So far I have:</p>

<p>HTML/CSS:</p>

<p><div class="snippet" data-lang="js" data-hide="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>.checkbox-custom {
  opacity: 0;
  position: absolute;
}
.checkbox-custom,
.checkbox-custom-label {
  display: inline-block;
  vertical-align: middle;
  margin: 5px;
  cursor: pointer;
}
.checkbox-custom + .checkbox-custom-label:before {
  content: '';
  background: #fff;
  border-radius: 5px;
  border: 2px solid #ddd;
  display: inline-block;
  vertical-align: middle;
  width: 10px;
  height: 10px;
  padding: 2px;
  margin-right: 10px;
  text-align: center;
}
.checkbox-custom:checked + .checkbox-custom-label:before {
  content: "";
  display: inline-block;
  width: 1px;
  height: 5px;
  border: solid blue;
  border-width: 0 3px 3px 0;
  transform: rotate(45deg);
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  border-radius: 0px;
  margin: 0px 15px 5px 5px;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;
  &lt;input id="checkbox-1" class="checkbox-custom" name="checkbox-1" type="checkbox"&gt;
  &lt;label for="checkbox-1" class="checkbox-custom-label"&gt;First Choice&lt;/label&gt;
&lt;/div&gt;
&lt;div&gt;
  &lt;input id="checkbox-2" class="checkbox-custom" name="checkbox-2" type="checkbox"&gt;
  &lt;label for="checkbox-2" class="checkbox-custom-label"&gt;Second Choice&lt;/label&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p>The <code>checked</code> checkbox should be a checkmark with the square bordered around it instead of just a checkmark. Searching for answers, I have only found cases where the checkmark is displayed using a UTF-8 character or an image. I am not able to use either of these for what I am trying to accomplish. I am only able to use plain CSS and HTML. Any suggestions?</p>

<p>codepen here: <a href="http://codepen.io/alisontague/pen/EPXagW?editors=110">http://codepen.io/alisontague/pen/EPXagW?editors=110</a></p>