JSFiddle - React, Tailwind, and code Playground

HTML

<div class="first">First</div>
<div class="second">second</div>

CSS

div{
  width:50%;
  background:blue;
  float:right;
  color:white
}
@media (max-width: 700px) {
  .first{
    background:red;
    float:none;
  }
  div{
    width:100%
  }
}