body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background-color: #fff;
    color: #333;
    transition: background-color 0.3s, color 0.3s;
}

body.dark-mode {
    background-color: #333;
    color: #fff;
}

#theme-toggle {
    position: fixed;
    top: 1rem;
    right: 1rem;
    padding: 0.5rem 1rem;
    font-size: 1rem;
    cursor: pointer;
    border: none;
    border-radius: 5px;
    background-color: #4CAF50;
    color: white;
}