/* Keeps input border blue after valid input */
input.form-control:valid {
    border-color: #007BFF; /* Bootstrap primary blue */
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}

/* Ensures filled (non-empty) inputs stay blue */
input.form-control:not(:placeholder-shown) {
    border-color: #007BFF;
    box-shadow: 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}