HTML,CSS,JAVASCRIPTでフローチャートを書く方法（Mermaid.js不使用）

フローチャート

<!DOCTYPE html>
<html lang="ja">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>フローチャート</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            background-color: #f9f9f9;
        }
        .chart {
            display: flex;
            justify-content: center;
            align-items: center;
            flex-direction: column;
            margin: 50px;
        }
        .box {
            background-color: #ffffff;
            border: 2px solid #007BFF;
            border-radius: 8px;
            padding: 20px;
            margin: 10px;
            width: 200px;
            text-align: center;
            position: relative;
        }
        .arrow {
            width: 0;
            height: 0;
            border-left: 15px solid transparent;
            border-right: 15px solid transparent;
            border-bottom: 20px solid #007BFF;
            margin: -10px 0;
        }
    </style>
</head>
<body>

<div class="chart">
    <div class="box">スタート</div>
    <div class="arrow"></div>
    <div class="box">処理A</div>
    <div class="arrow"></div>
    <div class="box">処理B</div>
    <div class="arrow"></div>
    <div class="box">エンド</div>
</div>

</body>
</html>

クラス図

<!DOCTYPE html>
<html lang="ja">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>クラス図</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            background-color: #f9f9f9;
        }
        .class {
            background-color: #ffffff;
            border: 2px solid #007BFF;
            border-radius: 8px;
            padding: 10px;
            margin: 20px;
            width: 200px;
            text-align: center;
            position: relative;
        }
        .class-name {
            font-weight: bold;
            border-bottom: 1px solid #007BFF;
            padding: 5px 0;
        }
        .attributes {
            margin: 5px 0;
            font-size: 14px;
            text-align: left;
        }
        .associations {
            font-size: 12px;
            position: absolute;
            bottom: -20px;
            left: 50%;
            transform: translateX(-50%);
        }
    </style>
</head>
<body>

<div style="display: flex; justify-content: center;">
    <div class="class">
        <div class="class-name">クラスA</div>
        <div class="attributes">- 属性1: 型<br>- 属性2: 型</div>
        <div class="associations">+ メソッド1()<br>+ メソッド2()</div>
    </div>

    <div class="class">
        <div class="class-name">クラスB</div>
        <div class="attributes">- 属性A: 型<br>- 属性B: 型</div>
        <div class="associations">+ メソッドA()<br>+ メソッドB()</div>
    </div>
</div>

</body>
</html>