JSFiddle - React, Tailwind, and code Playground

HTML

<table id="tiles">
    <tr><td></td><td></td><td></td><td></td><td></td></tr>
    <tr><td></td><td></td><td></td><td></td><td></td></tr>
    <tr><td></td><td></td><td></td><td></td><td></td></tr>
    <tr><td></td><td></td><td></td><td></td><td></td></tr>
    <tr><td></td><td></td><td></td><td></td><td></td></tr>
</table>
<div id="viewport"></div>

CSS

td {
    background: #e0e0e0;
    width: 50px;
    height: 50px;
    border: 1px solid #c0c0c0;
}

#viewport {
    width: 200px;
    height: 200px;
    border: 1px dashed blue;
    position: absolute;
    top: 20px;
    left: 20px;
}