We show what difference the CSS rule box-sizing border-box makes to your applications before showing the best way to apply border-box to your entire application while preserving the ability to render legacy components
That's a cool way to do it, specially on a reset like file. I'm currently avoiding all sorts of global selectors to avoid any conflicts on designs that do not follow a design convention or general rules, which happens a lot. I'd rather just give each components it's own rule and reuse components instead of styles.