How to create play button with border-radius?

Hi I'm trying to make a Pomodoro clock. I've made a play button by removing border-right and increasing border-left width to create a triangle.

My questions is - how do I apply border-radius to it?

https://codepen.io/jenlky/pen/ypQjPa?editors=1100

<div id="all-buttons" class="buttons"><!-- play button --><div id="play" class="play-button"></div><!-- pause button --><div id="pause"><div class="line-1"></div><div class="line-2"></div></div><!-- end of play and pause button--></div> .play-button {    z-index: 2;    width: 48px;    height: 48px;    border-style: solid;    border-width: 24px 0px 24px 48px;    border-color: white white white #FF8F83;}