@media only screen and (max-width: 768px) {
    .quantity {
        margin: 0px!important;
        padding: 0px;
        width: 100%!important;
        padding-bottom: 18px!important;
    }

    button.single_add_to_cart_button.button.alt {
        margin-bottom: 0px!important;
        padding-left: 10px;
        padding-right: 10px;
    }

    .quantity input {
        padding: 12px!important;
        width: 50px!important;
        height: 50px;
    }

    .woocommerce-variation-add-to-cart {
        margin-top: -10px!important;
    }
}