How do I set the border-radius of a highly adaptive toast to half the height?

want to use css to make a toast,border-radius that can automatically wrap lines according to the number of words is always half the height. Here is the code I wrote. Toast has become an oval. Help me see what the problem is

.
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>test</title>
    <style>
    * {
      margin: 0;
      padding: 0;
      -webkit-tap-highlight-color: transparent;
    }
    body{
      position: relative;
    }
    -sharptoast{
      position:fixed;
      left: 50vw;
      -webkit-transform: translateX(-50%);
      transform: translateX(-50%);
      bottom:10vw;
      width: max-content;
      max-width:80vw;
      line-height:10vw;
      font-size:20px;
      color:-sharpfff;
      background: rgba(0,0,0,.8);
      border-radius:50%;
      padding:5vw;
      margin:0 auto;
      z-index:9999;
    }
    </style>
  </head>
  <body>
    <div id="toast">toast</div>
  </body>
</html>
Jun.29,2022

set a maximum border-radius:999999px; demo

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