Widget change only in Main page

Question

I'm trying to add some margin on a Widget, but I want this to apply only on main page(html.site-main) and only on specific pixels. I guess I should use a media query.I searched for others with the same question but there was not any with the same question as mine but only similar ones. All I could do is gather some nonsense-code that is written bellow, hope you get what I want to do. Help please

@media screen and (max-width: 350px){
    html.site-main, #widget {
        margin-right: 250px!important;
    }
}

Answer 1

Okay...solved just by not using the 'html.site-main,' Instead it worked like this '.home #widget'