<!-- :empty -->
<section class="example-cntr empty">
    <h1>CSS <code>:empty</code> pseudo-class</h1>
    <p>The <code>:empty</code> pseudo-class targets elements that have no content of any kind in them, at all.</p>
    <p>If it has any type of character, even a space, then the element is <span class="underline">not</span> considered empty.</p>
    <p>In the following example <span class="red">Red</span> boxes have content and <span class="yellow">Yellow</span> boxes are empty:</p>
    <div class="flex-ctnr">
        <div>I have content, thus I'm red…</div>
        <div> </div> <!-- A space is considered content so it’s red -->
        <div></div> <!-- Totally empty element so it’s yellow -->
        <div><!-- This comment inside isn’t considered content so it’s yellow --></div>
    </div>
</section>

//:empty
.empty {
    .flex-ctnr div {
        display: flex;
        flex: 1;
        justify-content: center;
        align-items: center;
        margin: 0 5px;
        padding: 3px;
        background: $r;
    }
    .flex-ctnr div:empty { background: $y; }  
}


//Styling stuff not needed for demo
body { text-align: left; }
.example-cntr {
    max-width: 800px;
    margin: auto;
    padding: 20px 50px;
    box-shadow: 0 1px 2px rgba(black,.3);
    background: rgba(black,.15);    
}
h1 {
    text-transform: none;
    border-bottom: #636363 1px dotted;
    code {
        display: inline-block;
        margin-bottom: 10px;
        color: $y;
        background: none;
        box-shadow: none;
    }
}
.flex-ctnr {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    margin-bottom: 20px;
}
code { font-size: 1em; }
.underline { text-decoration: underline; }
$r: lighten($r,12);
.red { color: $r; }
.green { color: $g; }
.yellow { color: $y; }