https://jsfiddle.net/kshatriiya/fhbqqmxc/1/
<div id="play-area">
<div id="play-area-overlay">
<div id="textbox">
<h2>
Welcolme.
</h2>
</div>
<div id="visualizer">
</div>
</div>
</div>
</div>
CSS:
#play-area {
position: relative;
width: 100vw;
height: 400px;
margin: 0 auto;
}
#play-area-overlay {
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
height: 100%;
margin: 0px;
width: 100%;
}
#textbox {
height: 100%;
width: 400px;
margin: 0px;
}
#visualizer {
height: 100%;
width: 50%;
margin: 0px;
}