JSFiddle - React, Tailwind, and code Playground

HTML

<div class="Table" id="planner">

  <div id="room_207" class="row">
    <div class="cell disabled-element" style="">207</div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
  </div>
  <div id="room_208" class="row">
    <div class="cell disabled-element" style="">208</div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell busy" data-group_id="$1$6ARlIJCw$0.QtZXQF4DwyIyd0s4cnp/"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
  </div>
  <div id="room_209" class="row">
    <div class="cell disabled-element" style="">209</div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell free"></div>
    <div class="cell busy" data-group_id="$1$6ARlIJCw$0.QtZXQF4DwyIyd0s4cnp/"></div>
   ...

CSS

.Table
{
   display: table;
   -webkit-box-sizing:border-box;
   -moz-box-sizing:border-box;
   box-sizing:border-box;

   border-collapse:collapse;
}

.row
{
   display: table-row;
}

.cell
{
   display: table-cell;
   border: solid 1px blue;
   background:#C8CACC;
   width:35px;
   height:12px;
   font-size:1px;
   overflow:hidden;
   line-height:1em;
   vertical-align:middle;
}

.cell.busy
{
    background:red;
}