CSS styling checkbox when checked - not working

The CSS is fine. Your problem is matching the label elements with the input elements.

This method relies on the fact that clicking the label toggles the checkbox. If the label isn't attatched to the checkbox it won't work. Match the value of each label's for attribute to the id of each checkbox.

For example:

<input type="checkbox" class="input-checkbox" id="checkbox1">
<label for="checkbox1" class="input-label"></label>

LIVE EXAMPLE HERE