Yes all made in Twine! Mainly fiddling with HTML classes and CSS rules to get the whole thing working.
Though, this was done with the SugarCube format, rather than the base Harlowe, the first allowing for more customisation than the latter.

But I've answered coding questions on my dev Blog and on the Twine discord too. If you are looking for resources, I've compiled an extensive list here :)

I'd love to participate in more fun jams like this. This was really fun to do!