changing the size of a video for mobile

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

Hi there, I am having some issues trying to change the size of my video that's on my home page for mobile. It looks great on desktop, and the height of the section is large. 

When I switch to mobile it was too big and I have tried to change it to medium which looks perfect on mobile, but it ends up changing it for the entire site.

Can anyone help with some custom CSS.

Thanks everyone

It looks like you solved with this CSS?

@media screen and (max-width: 640px) {
    .homepage section:first-child {
        height:60vh !important;
        min-height: unset !important
    }
}