JSFiddle - React, Tailwind, and code Playground

HTML

<div class="animated-box">Animated box</div>

CSS

.animated-box {
    border:2px solid #bada55;
    border-radius: 10px 0;
    
    color: #bada55;
    font-size: 20px;
    line-height:20px;
    font-weight:bold;
    text-align:center;
    
    padding:50px;
    width:200px;
    
    -webkit-animation:fontbulger 4s infinite;
    -moz-animation:   fontbulger 4s infinite;
    -o-animation:     fontbulger 4s infinite;
    animation:        fontbulger 4s infinite;
}

@-webkit-keyframes fontbulger {
  0%, 100% {
    font-size: 15px;
  }
  50% {
    font-size: 20px;
  }
}
@-moz-keyframes fontbulger {
  0%, 100% {
    font-size: 15px;
  }
  50% {
    font-size: 20px;
  }
}
@-o-keyframes fontbulger {
  0%, 100% {
    font-size: 15px;
  }
  50% {
    font-size: 20px;
  }
}
@keyframes fontbulger {
  0%, 100% {
    font-size: 15px;
  }
  50% {
    font-size: 20px;
  }
}