body
{
<!--background-image: url(../images/fondo.jpg);-->
background-size: 100vw 100vh;
background-attachment: fixed;
margin: 0;
font-family: monospace;
}
form
{
    width: 450px;
    margin: auto;
    background: rgba(0,0,0,0.4);
    padding: 10px 20px;
    box-sizing: border-box;
    margin-top: 60px;
    border-radius: 7px;  
}
h2
{
    color: #fff;
    text-align:center;
    margin: 0;
    font-size: 30px;
    margin-bottom: 20px;
}
input, textarea
{
width:100%;
margin-bottom: 20px;
padding: 7px;
box-sizing: border-box;
font-size: 17px;
border: none;

}
textarea
{
    min-height: 100px;
    max-height: 200px;
    max-width: 100%

}
#boton
{
    background: #31384A;
    color:#fff;
    padding:20px;

}
#boton: hover
{
    cursor:pointer;
}

@media (max-width:480px)
{
    form
    {
        width:100%;
    }
}