:root {
            color-scheme: dark;
        }
        body {
            font-family: Arial, sans-serif;
            margin: 0;
        }
        .light {
            background-color: #f9f9f9;
            color: #222;
        }
        .light table {
            background: white;
            color: #000;
        }
        .container {
            padding: 20px;
        }
        h1 {
            text-align: center;
        }
        table {
            width: 100%;
            border-collapse: collapse;
            margin-top: 1em;
        }
        th, td {
            border: 1px solid #333;
            padding: 8px;
            text-align: center;
        }
        th {
            background: #333;
        }
        .light th {
            background: #007BFF;
            color: white;
        }
        tr:nth-child(even) {
            background: #1e1e1e;
        }
        .light tr:nth-child(even) {
            background: #f0f0f0;
        }
        .theme-toggle {
            display: flex;
            justify-content: center;
            margin-top: 1em;
        }
        .mastered {
            color: #00ff00;
            font-weight: bold;
        }
        button {
            background: #444;
            color: white;
            padding: 6px 12px;
            border: none;
            cursor: pointer;
            border-radius: 6px;
        }
        .light button {
            background: #ccc;
            color: #222;
        }
    table td:nth-child(3),
    table th:nth-child(3) {
        display: none;
    }



thead th {
      position: sticky;
      top: 0;
      background: white;
      z-index: 1;
      color: black;
    }