As an aside it's also using TailwindCSS 2.1 with the JIT compiler enabled.
What's your take on Tailwind so far? I've found the lack of a react offering has really slowed me down.
It's working out well for the most part, but I don't use React.
I mainly develop server rendered apps and sprinkle in JS as needed.
The only weak link with Tailwind IMO is the lack of JS for doing common things like hiding / showing menus, tooltips, modals, tabs and other stuff you'd find baked into Bootstrap. I know there's some JS included in the TailwindUI components but it's not for JS libraries that I use. I prefer using StimulusJS which isn't something they support at the moment.
Fortunately there's a bunch of StimulusJS Tailwind examples provided by the community so it's not too bad in the end.
I imagine it's hard for Adam because there's React, Vue, Alpine and StimulusJS, all of which are popular enough where there's a good amount of users using them. I'm optimistic that he'll think of a way to cater to all of these users in some way, it'll only be a matter of time. NOTE: This is just speculation, I'm not affiliated with Tailwind in any way.
TailwindCSS is open source and free. It's at https://tailwindcss.com/.
TailwindUI is an optional paid product that has a bunch of pre-made TailwindCSS components created by the makers of TailwindCSS. Basically pre-made widgets and layouts.
TailwindUI has a few free components too (no signups required) at https://tailwindui.com/preview.
And if you Google around for Tailwind components and themes you'll be able to find a bunch. It's just CSS at the end of the day so there's lots of community driven examples. For example here's a bunch of free ones at https://tailwindcomponents.com/components, https://www.tailwindtoolbox.com/starter-templates and more at https://github.com/aniftyco/awesome-tailwindcss#ui-libraries....