Will amp-story work fully with Normalize.css and Basscss? I ask because AMP Start is built on top of these two existing open-source projects:
https://www.ampstart.com/howitworks
Normalize.css
Normalize.css makes browsers render all elements more consistently and in line with modern standards. It precisely targets only the styles that need normalizing. This provides a clean slate to define clear and consistent styles for AMP Start across devices.
Basscss
AMP start is built using Basscss, a low level CSS toolkit. Basscss is a very light weight toolkit, that provides lots of CSS utility classes help us do things like layouts, responsive Grids etc, without having to write any custom css.
Basscss was out-of-the-box lean and responsive, which was important for AMP Start. We used Basscss as the base (sans addons) but we removed any instances of “!important” from CSS rules because "!important" is incompatible with AMP. By using the existing Basscss classes, we were able to write a lot less CSS and still make great looking pages, even with AMP’s 50Kb CSS limitation.
On top of the foundation provided by these two projects, we added a set of more opinionated styles to the CSS, so that the components and templates would inherit a consistent look for AMP Start.
All told, the CSS takes up less than half of the 50kB quota in AMP, so you should have plenty of room to customize your pages with Basscss and AMP Start classes.
Yes, these both result in plain CSS, which can be used in amp-story. Like all AMP documents, the CSS will need to be inlined, in the <style amp-custom> block.
See the "Add styles to a page" section of the AMP Style & layout documentation.