#callback_form_button_id {
    position: relative;
}
#callback_form_button_id * {
    transition: opacity 0.3s ease-in;
}
#callback_form_button_id .loader {
    position: absolute;
    display: block;
    fill: transparent;
    top: calc(50% - 0.75rem);
    left: calc(50% - 0.75rem);
    width: 1.5rem;
    height: 1.5rem;
    animation: rotating 1.5s linear infinite;
    display: none;
    opacity: 0;
}
#callback_form_button_id.loading span {
    color: transparent;
    opacity: 0;
}
#callback_form_button_id.loading .loader {
    fill: transparent;
    display: block;
    opacity: 1;
}

@-webkit-keyframes rotating {
    0% {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(1turn);
    }
}
@keyframes rotating {
    0% {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(1turn);
    }
}
#form_display_flex{
    display:flex;
}