section {
    background-color: #f8f9fa;
    border-radius: 6px;
}

input.required.empty,
select.required.empty {
    border-width: 1px;
    border-color: red;
}

.required-checkbox {
    padding: 15px;
    margin: -15px;
    border-radius: 6px;
}

.required-checkbox.empty {
    border: 1px solid red;
}