style.css

#r {
    width: 100%;
}

label{
    color: darkgreen;
}

input{
    color: darkgreen;
}

select{
    color: darkgreen;
}

div {
    border: 1px solid darkgreen;
    width: 50%;
    margin: auto;
}

table {
    margin: auto;
}

.error {
    text-align: center;
    color: red;
}

.result {
    text-align: center;
    color: black;
}