.g-recaptcha {
    margin-right: auto;
    margin-left: auto;
    text-align: center;
    width: 300px;
}

@media screen and (max-width: 480px) {
    .g-recaptcha {
        transform-origin: 0% 0%;
        transform: scale(0.85);
        width: 258px;
    }
}