I wouldn't say it's a hostile platform, I'd say that it's a volatile design medium. Regarding breakpoints, I've always agreed with Jeremy Keith's opinion on the

I wouldn't say it's a hostile platform, I'd say that it's a volatile design medium. Regarding breakpoints, I've always agreed with Jeremy Keith's opinion on the subject, which in some sense is to design for the content and fix it when it breaks, but to assume that it will and test it as best as you can. Breakpoints are just a way of demarcating broken/not-broken layout. I also use them for generalizing design if I'm doing it before writing the layout in code, which you can do if you start with no assumptions as to how it will be viewed, and just choose some arbitrary constraints to move things around within, then refine when you actually have something in the browser.