JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    Crotte
    <div class="pouet">
        <div class="menu">ZUT</div>
    </div>
    <div class="pouetClear"></div>
    De Bique
</div>

CSS

.container {
    width:100%;
    max-width : 640px;
    min-height:250px;
    margin:auto;
    background:#cde;
}
.menu {
    width:100%;
    max-width : 640px;
    margin:auto;
    background:#dec;
}
@media (min-width: 640px) {
    .pouet{
        position:absolute;
        left:0;
        width:100%;
        background:#ecd;
        height:30px; /* berk */
    }
    .pouetClear{
        height:30px; /* berk */
    
    }
}