form.css

* {
    box-sizing: border-box;
}

input, select, textarea{
    width: 100;
    padding: 12px;
    border: 1px solid #ccc;
    border-radius: 5px;
    resize: vertical;
}

label {
    padding: 12px 12px 12px 0;
    display: inline-block;
}

input[type=submit]{
    background-color: rgb(128, 93, 162);
    color: white;
    padding: 12px 20px;
    border: none;
    border-radius: 5px;
    float: right;
}

.contenedor{
    border-radius: 5px;
    background-color: rgb(66, 110, 176);
    padding: 20px;
}

.col-30{
    float: left;
    width: 30%;
    margin-top: 6px;
}

.col-70{
    float: left;
    width: 70%;
    margin-top: 6px;
}

.fila:after{
    content: "";
    display: table;
    clear: both;
}

@media screen and (max-width: 600px){
    .col-30, .col-70, input[type=submit]{
        width: 100%;
        margin-top: 0;
    }

}