body {
    font-family: Arial, sans-serif;
    margin: 20px;
    background-color: #f4f4f4;
}

h1 {
    text-align: center;
    color: #333;
}

.question {
    background-color: #fff;
    padding: 15px;
    margin-bottom: 15px;
    border-radius: 5px;
    border: 2px solid #4CAF50;
}

.question h2 {
    color: #4CAF50;
    font-size: 1.3em;
}

.question .correct-answer {
    color: #4CAF50;
    font-weight: bold;
}

.question .demonstration {
    font-style: italic;
    margin-top: 10px;
}

.question .detailed-solution {
    margin-top: 10px;
    padding-left: 20px;
}

.footer {
    text-align: center;
    margin-top: 30px;
    font-size: 1em;
    color: #333;
}

.btn {
    background-color: #4CAF50;
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    text-decoration: none;
    font-size: 1.1em;
}

.btn:hover {
    background-color: #45a049;
}