Centre align gallery for mobile view

Site URL: https://www.globalstagestreams.com/

Hi,

I'd like to add some CSS code so that the gallery near the bottom of the site centre aligns when viewed on mobile. It looks fine on desktop with the 5 images in a row but when I view the site on mobile the last image of the gallery is aligned to the left. Can anyone tell me what code I'd need?

Thanks

https://www.globalstagestreams.com/

password: global1

Add to Home > Design > Custom CSS

@media screen and (max-width:640px) {
div#block-yui_3_17_2_1_1587658163210_68106 .sqs-gallery .slide:last-child {
    width: 100% !important;
    clear: left !important;
    text-align: center;
}
}