JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
  <title>Флаг Японии</title>
  <style>
   .japan {width: 300px; 
         height: 200px;
         border: 2px solid #ccc;
         background: radial-gradient(circle, #bc002d 58px, #fff 60px);
    </style>
 </head>
 <body>
  <div class="japan"></div>
 </body>
</html>