Thoughts
Compose screen still looks a little weird, like I'm just typing characters into the middle of an otherwise green page
and I have no idea when I'm going to hit 140 characters, but overall I'm very happy with the CSS. While this wasn't mobile-first design per-se, it was definitely designed with the idea that it was going to have to work well on mobile, so no sidebar or anything. I have like 10 color schemes I tried that are commented out in the CSS for you to play with, and I still don't love what I ended up with, but the 3-color CSS variable set up makes it addicting-ly easy to change. It will switch to a dark color scheme with an ugly yellow if your browser requests it, which Vivaldi apparently doesn't, so I'll have to work on that.