body {
    background-color: #f0f2f5;
    font-family: 'Segoe UI', sans-serif;
}
.card {
    border-radius: 1rem;
    overflow: hidden;
}
.btn-success {
    background-color: #28a745;
    border: none;
    font-weight: bold;
}
.btn-dark {
    background-color: #1a1a1a;
}
#resultadoGratis {
    border: 2px solid #0d6efd;
}