index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link
    rel="stylesheet"
    href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.1/normalize.min.css"
  />
  <title>Zenn</title>
</head>
<body>
  <style>
    #wrap {
      max-width: 960px;
      margin: 0 auto;
      height: calc(100vh - 100px);
    }
    #main {
      width: 100%;
      height: 100%;
      display: flex;
      flex-direction: column;
    }
    .tool {
      
    }
    .demo {
      flex: 1;
      max-height: calc(100% - 24px);
    }
  </style>
  <div id="wrap">
    <h2>React Split MDE</h2>
    <div id="main"></div>
  </div>
  <script src="./main.js"></script>
</body>
</html>