.form-step {
    display: none;
}
.form-step.active {
    display: block;
}
.progress-bar {
    margin-bottom: 20px;
}
.btn-next, .btn-prev {
    margin-top: 20px;
}
.alert {
    margin-top: 20px;
}
.is-invalid {
    border-color: red;
}

.invalid-feedback {
    display: none;
    color: red;
    font-size: 0.875em;
}

.form-control:invalid + .invalid-feedback {
    display: block;
}