JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="bar">TITLE</div>
    <div id="main">
        <div id="maincontainer">
            <div class="itemcontainer" id="item1">
                <div class="under">
                    <a href="#main"><div class="half"></div></a>
                    <a href="#item2"><div class="half"></div></a>
                </div>
                <div class="item">
                    <div class="itemtitle">
                        ITEM 1
                    </div>
                    <div class="img">
                        IMG 1
                    </div>
                    <div class="img">
                        IMG 2
                    </div>
                    <div class="img">
                        IMG 3
                    </div>
                    <div class="img">
                        IMG 4
                    </div>
                </div>
            </div>
            <div class="itemcontainer" id="item2">
                <div class="under">
                    <a href="#item1"><div class="half"></div></a>
                    <a href="#item3"><div class="half"></div></a>
                </div>
                <div class="item">
                    <div class="itemtitle">
                        ITEM 2
                    </div>
                    <div class="img">
                        IMG 1
                    </div>
                    <div class="img">
                        IMG 2
                    </div>
                    <div class="img">
                        IMG 3
                    </div>
                    <div class="img">
                        IMG 4
                    </div>
                </div>
            </div>
            <div class="itemcontainer" id="item3">
                <div class="under">
                    <a href="#item2"><div class="half"></div></a>
                    <a href="#"><div class="half"></div></a>
                </div>
                <div class="item">
                    <div...

CSS

body, html {
    height: 100%;
    margin: 0;
}

#bar {
    z-index:90;
    position: fixed;
    width: 50px;
    height: 100%;
    background: #47B;
}

#main {
    z-index:10;
    padding-left: 50px;
    width: auto;
    height: 100%;
    background-color: #AAB;
    overflow-x: auto;
    overflow-y: hidden;
    overflow : -moz-scrollbars-horizontal;
}

#maincontainer {
    z-index:20;
    height: 100%;
    text-align: center;
    white-space: nowrap;
}

.itemcontainer {
    z-index:30;
    position: relative;
    display: inline-block;
    height: 100%;
    width: 600px;
    background-color: #99A;
}

.under {
    z-index: 70;
    width: 100%;
    height: 100%;
}

.under a{
    z-index: 71;
    display: block;
    height: 100%;
    width: 50%;
    float: left;
}

.under a:hover {
    background: #AAB;
}

.item {
    position: absolute;
    top:0;
    left:0;
    height: 100%;
    padding: 20px 0;
}

.img {
    z-index: 80;
    width: 500px;
    height: 300px;
    background: #fff;
    margin: 30px 50px;
}