estilo.css

body{
    background: url(./matematica.jpg);
    font: normal 15pt Arial;
    background-size: 150%;
    background-position: fixed;
}

header{
    color: white;
    text-align: center;
    text-shadow: 2px 2px 10px black;
    font-family: 'Mate SC', serif;
}

section{
    background: rgb(2, 72, 11) ;
    border-radius: 10px;
    padding: 15px;
    width: 500px;
    margin: auto;
    box-shadow: 2px 2px 10px rgb(0, 0, 0);
    color: white;
    font-family: 'Mate SC', serif;
}

footer{
    color: white;
    text-align: center;
    font-style: italic;
    font-size: 11pt;
    padding: 24px
}
input{
    border-radius: 10%;
    font-family: 'Mate SC', serif;
    font-size: 18px;
}
div#sel{
    text-align: center;
}
select{
    text-align: center;
    padding-left: 20px;
    padding-right: 10px;
    font-size: 15px;
}