body {background-color:black; font-family: arial; color:white;}
h1{color:grey; font-family:verdana; text-align: center;}

.maindiv {
    background-color: white;
    color: black;
    width: 500px;
    padding: 20px;
    border-radius: 25px;
    margin: auto;
}

.elem{
    width: 250px;
    margin: auto;
}
footer{
    text-align: left;
    margin: 10px;
    
}

#principal {
    margin:5px;
    margin-left: 10px;
}

#rate {
    margin: 5px;
    margin-left: 10px;
}

#years {
    margin: 5px;
    margin-left: 10px;
}