Flexbox grid test.

HTML

<div class="container">
    <div class="flex-container">
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
        <div class="box"></div>
    </div>
</div>

CSS

.flex-container {
    margin-right: -16px;    
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

.box {
    width: 96px;
    height: 72px;
    background-color: #eee;
    margin-right: 16px;
    margin-bottom: 64px;
}

@media (max-width: 480px) {
    .flex-container {
        margin-right: 0;
        justify-content: center;
        background-color: #f00;
    }

    .box {
        margin-left: 16px;
    }
}