Nice. But in my experience, front-end design always requires some hacks here and there, e.g. because of compatibility issues or because of design flaws in CSS. So either the Stripe engineers are ridiculously clever, or they are just avoiding the difficult stuff.
Their work is really about as good as it gets, so I don't really see how you could conclude they are "avoiding the difficult stuff" - though quite possibly they don't care very much how their pages render in IE 11 (I don't know!).
