JSFiddle - React, Tailwind, and code Playground

HTML

<div id="titlebar">
    <p> Activities </p>
    <blink style="display: block; text-align: center; margin-top: -1.4em;"> 12:00 </blink>
    <p style="text-align: right; margin-top: -1.4em;"> Jasper St. Pierre </p>
</div>

<div id="accordion">
    <div class="decoration"> Firefox </div>
    <div class="window"> Firefox Window Contents </div>
    <div class="decoration selected"> File Manager </div>
    <div class="window selected"> File Manager Window Contents </div>
</div>

CSS

html, body, p {
    margin: 0;
    padding: 0;
    border: 0;
}

html, body {
    height: 100%;
    font-family: sans;
    font-weight: bold;
}

#titlebar {
    background-color: black;
    height: 1.4em;
    line-height: 1.4;
    padding: .24em 1em;
    color: #ccc;
}

.decoration {
    cursor: pointer;
    color: #222;
    text-shadow: 1px 1px 0px white;
    border-bottom: 1px solid white;
    background-color: #e4e4e4;
    background-image: -moz-linear-gradient(#efefef 0%, #e4e4e4 100%);
    height: 2em;
    line-height: 2;
    text-align: center;
}

.window {
    display: block;
    text-align: center;
}

#accordion {
    border-radius: 15px 15px 0 0;
    position: absolute;
    top: 1.84em;
    bottom: 0px;
    width: 100%;
}

JavaScript

var inWindowSelect = false;

$("#titlebar").mouseenter(function() {        
    inWindowSelect = true;
    $(".decoration").slideDown("fast").click(function() {
        if (!inWindowSelect) return;
        $(".decoration, .window").removeClass("selected");
        $([this, $(this).next()[0]]).addClass("selected").detach().appendTo("#accordion").slideDown();
        $(".decoration:not(.selected), .window:not(.selected)").slideUp();
    });
});

$(".decoration:not(.selected), .window:not(.selected)").hide();