JSFiddle - React, Tailwind, and code Playground

HTML

<div class="border"> <button type="button" class="red">Click Me!</button> </div>
<br><br>
<ul class="border-left">
  <li class="border-top">
    <div class="red">coucou</div>
  </li>
</ul>

CSS

.border {
  border:1px solid blue;
}
.border-left {
  border-left:1px solid blue;
}
.border-top {
  border-top:1px solid blue;
}
ul, li {
  list-style : none inside;
  padding: 0;
  margin : 0;
  display: block;
}
.red {
  background: red;
  border: none;
  display:block;
}