JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <button class='button' id="clicked" onclick="onToggle()"></button>
  <span class="text-1">Play</span>
  <span class="text-2">Pause</span>
</div>

CSS

.container {
  padding: 10px;
  border: 1px solid;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s linear;
}

.text-1, .text-2 {
  display: none;
}

.button {
  border: 0;
  background: transparent;
  box-sizing: border-box;
  width: 0;
  height: 20px;
  border-color: transparent transparent transparent #202020;
  transition: 100ms all ease;
  cursor: pointer;
  border-style: solid;
  border-width: 10px 0 10px 20px;
  padding: 0
}

.button.paused {
  border-style: double;
  border-width: 0px 0 0px 20px;
}


.pauseicon{
    border-left: 10px solid #000;
    border-right: 10px solid #000;
    width: 10px;
    height: 25px;
}

.button:hover {
  border-color: transparent transparent transparent #404040;
}

.button:hover + .text-1 {
  display: inline;
}

.pauseicon:hover ~ .text-2 {
  display: inline;
}

JavaScript

function onToggle() {
	document.getElementById("clicked").classList.toggle("button");
  document.getElementById("clicked").classList.toggle("pauseicon");
}