Ask HN: Recommend a Lightweight Responsive CSS Framework for 2016?

It's been a few years since I've done significant work in stylesheets, and while I feel up to date on SASS and CSS itself, I have no idea what's going on in the framework world. I'm now beginning a very small side project which unsurprisingly needs a web UI. I don't want to spend a ton of time testing CSS a role browsers and devices, but something like Bootstrap seems hugely bloated for this tiny project. What mature, lightweight, well-maintained responsive stylesheet framework would you recommend? I'd prefer something with a strong community if possible, and semantic naming conventions would be a nice bonus.