I guess the OP is assuming everyone knows the Bootstrap convention and so it's just skipping past the bull, so to speak, and showing you the goods. Unfortunately, right now, it's showing the UI elements in exactly the way one would do so to show the weaknesses of flat UI. I think the juxtaposition of the buttons and the menubars floating in space is especially problematic, because it's too easy to think "buttons, more buttons, big extra long buttons"

And then this is immediately followed by the Input elements which, after seeing the first two sections, look just like buttons with a white background and different text-alignment...that's also an unfortunate arrangement.

Anyway, I hate to bag on something that's a proof of concept (and an attractive one at that) and wasn't intended to be as thoroughly documented as Bootstrap...I'm just pointing out that this particular arrangement is more confusing than it needs to be.