How can I change the background of a parent <div> when an <input> or <a> is :focus'd (or any other dynamic pseudo-class?

Eg

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How can I change the background of a parent <div> when an <input> or <a> is :focus'd (or any other dynamic pseudo-class?

Eg

<div id="formspace">
<form>
<label for="question">
How do I select #formspace for the case when a child is active?</label>
<input type="text" id="question" name="answer"/></form></div>