Solution using HTML and CSS only. Any help apreciated!

Hello there! This is my 3rd challenge. I think I got it fine, but any help to improve is appreciated! I do have a question though, when I tried to apply the "box-radius" property to ".summary-box", for some reason it wouldn't let me, but it did let me use it on ".main-box", why is that? Also the boldness of the font isn't exactly the same, but I think it's because I didn't download the correct font or something. Also it's my first time doing "@media" stuff, did I write it correctly? Thanks!