JSFiddle - React, Tailwind, and code Playground

HTML

<div style="position:relative">
<div class="cell " style="left: 20px; top: 20px;">&nbsp;</div>
<div class="cell on" style="left: 20px; top: 40px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 60px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 80px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 100px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 120px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 140px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 160px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 180px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 200px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 220px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 240px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 260px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 280px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 300px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 320px;">&nbsp;</div>
<div class="cell " style="left: 20px; top: 340px;">&nbsp;</div>
<div class="cell on" style="left: 40px; top: 20px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 40px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 60px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 80px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 100px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 120px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 140px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 160px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 180px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 200px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 220px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 240px;">&nbsp;</div>
<div class="cell " style="left: 40px; top: 260px;">&nbsp;</div>
<div class="cell " style="left: 40px; top:...

CSS

.cell {
    border: 2px solid black;
    width: 18px;
    height: 18px;
    position: absolute;
    
}
.on {
    background-color: #999;
}