label,
input[type='submit'] {
    display: block;
    margin: 1rem 0 .5rem;
}

input:invalid + span:after {
    color: red;
    content: '✖';
    padding-left: 5px;
}

input:valid + span:after {
    color: green;
    content: '✓';
    padding-left: 5px;
}