Ask HN: What's the best minimal CSS framework?

Hello HN, I'm a backend programmer and it's been quite some time since I worked with anything frontend related. I'm not bootstrapping a quick project, kind of prototype to "throw" out there and see what is the feedback. Meaning that I know very little about CSS and I don't really want to spend days trying to learn how to properly use complex fancy tools. I'm looking for a basic grid system (possible responsive), a few buttons, forms, and so on - the usual stuff CSS frameworks are done for. Bootstrap and Foundation would be my default choice but they cause a bit of a overhead. Is there any minimal framework out there that would speed up the process? Maybe based on bootstrap or foundation, just simpler. Thanks in advance