Hi lormayna, I'm the creator of Picnic CSS, thanks for considering it! If you don't mind me asking, why did you consider using Picnic and why wouldn't you choose using it? I'm trying to improve it constantly and I'd really appreciate your opinion from the point of view of "learning web development" (:
If you have any question you can just reach me here or on github
When going to http://picnicss.com/documentation#checkbox on an iPhone (iOS 9.2.1), the checkmark doesn't hide when it's unchecked; it just gets bigger. So on your example, the default selected boxes just look like they have big checkmarks in them. Sorry I don't have the time to write an issue at the moment.
a responsive grid that handles nesting is very difficult to do across the majority of devices. I ended up going with bootstrap after trying to find a minimal css framework that would handle all the different edge cases.
100% agree. Right now I'm deprecating the current grid based on ungrid in favor of a better float based grid [1]. I completely believe you, the most painful thing (maybe the only one?) for Picnic was definitely the grid, too many edges, no good model in css (and don't get me started on flexbox [2]).
If you have any question you can just reach me here or on github