JSFiddle - React, Tailwind, and code Playground

by core972

HTML

<div id="waiting"></div>

CSS

#waiting {
  position: relative;
  margin: 5rem;
  height: 3rem;
  width: 50vw;
  background: #c0ff95;
}
#waiting::after {
  position: absolute;
  bottom: 0;
  content: "";
  height: 0.5rem;
  background-color: #333;
  width: 100%;
  animation: 2s linear 0s infinite alternate wait;
}

@keyframes wait {
  0% {
    width: 0;
  }
  25% {
    width: 100%;
    transform-origin: right center;
  }
  50% {
    width: 0;
    transform-origin: right center;
  }
  75% {
    width: 100%;
  }
  100% {
    width: 0;
  }
}