body {
    font-family: Arial, sans-serif;
    background: #f2f2f2;
    text-align: center;
    padding: 20px;
}

.menu {
    margin-top: 40px;
}

.botao {
    display: block;
    margin: 15px auto;
    padding: 20px;
    width: 200px;
    background: #222;
    color: #fff;
    text-decoration: none;
    font-size: 18px;
    border-radius: 8px;
}

.botao:hover {
    background: #444;
}

.exercicio {
    background: #fff;
    padding: 15px;
    margin: 15px auto;
    max-width: 400px;
    border-radius: 8px;
}

.exercicio img {
    max-width: 100%;
}

.voltar {
    display: inline-block;
    margin-bottom: 20px;
    text-decoration: none;
}