It's really not as difficult as it is being made. This down to "what you need to do to make something stand out", which means sorting out the importance of ele

It's really not as difficult as it is being made. This down to "what you need to do to make something stand out", which means sorting out the importance of elements and turning that into a hierarchy. While there's no way to argue their results, there are plenty of reasons to argue their sampled materials. Flat design doesn't mean turning a button into an outline. And I'm willing to bet the button would've performed just as well without the skuemorphic gradient, but WITH the solid background colour instead of becoming an outline. Same with every single other implementation. They mis-implemented a design code. To come back to my initial point; it's all about hierarchy. In any interface (wether on paper or on a screen) you need to direct a person's attention. This is done by visually prioritising elements. And there are a tonne of ways to do so. A gradient. An inverted colourscheme. An angle. A wording difference. A texture. Bold. Underline. Etc - I'm sure we could all go on for ages coming up with other ways. TLDR: Disagree with their definition of "flat design", or the (exceedingly poor) way flat design was implemented in the examples they gave.