JSFiddle - React, Tailwind, and code Playground

by Ankhena

HTML

<div class="line">

</div>

CSS

* {
  box-sizing: border-box
}

html,
body {
  height: 100%;
  padding: 0;
  margin: 0;
}

.line {
  position: relative;
  width: 100px;
  height: 5px;
  background: #999;
  margin: 30px;
}
.line::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  width: 0;
  height: 5px;
  background: #f00;
  animation: animate 3s linear;
  
}
@keyframes animate {
 from { width: 0; }
 to { width: 100%; }
}