<!DOCTYPE html>
<html>
<head>
  <title>iframe sandbox</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      font-family: system-ui, -apple-system, sans-serif;
      padding: 20px;
      max-width: 1200px;
      margin: 0 auto;
    }

    .container {
      display: flex;
      gap: 20px;
      margin-bottom: 20px;
    }

    @media (max-width: 768px) {
      .container {
        flex-direction: column;
      }
    }

    .editor {
      flex: 1;
 