#main{
    display: flex;
    justify-content: center;
}
form{
     -webkit-align-items: center;
    -moz-align-items: center;
    -ms-align-items: center;
    align-items: center;
    display: -webkit-box;
    display: -moz-box;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
    -webkit-justify-content: center;
    -moz-justify-content: center;
    -ms-justify-content: center;
    justify-content: center;
    margin-bottom: 30px;
    font-size: x-large;
    flex-direction: column;
    border:#3ca55c 5px solid;
    border-radius: 25px;
    background-color: white;
    width: 50%;
}
Form > input{
    padding:5px;
    background: wheat;
    font-size: large;
    -webkit-border-radius: 10px;
    -moz-border-radius: 10px;
    border-radius: 10px;
    margin: 10px;
}