I really love this, and I'd love to do something similar for my projects, but I don't know where to start looking for ressources or data about this(I mean, I could just rip their CSS and html, but I'd like to do it cleanly) It's kinda reminding me of bootstrap, but in a more modern style.

Is there some "guidelines" that I can follow to achieve this kind of look? or some kind of basic template that I can start working on?are they using some kind of libraries or framework for this? or is this just a design/"artistic" trend for recent startups?