For added fun, you can try switching between different databases:

http://static.wiki/en/United_States

http://static.wiki/zh/美国

http://static.wiki/fr/United_States

http://static.wiki/enwikiquote/United_States

http://static.wiki/simple/United_States

Is there a way to get this simple theme / stylesheet to work for the regular Wikipedia? I really like it.

Thank you. Unfortunately, you'd have to write that stylesheet from scratch. For this demo, I just wrote them in the Svelte components.

Is the db in memory?

sql.js is in memory, but the database file is only partially loaded from the static file host.

No, as other comments have noted it's stored in S3.