An arch that opens over a living scene

Build one interactive web page: A real CSS mask, scrubbed by scroll, opens onto a layered parallax scene with shimmering water, a day and night switch, story pins and a letter-by-letter lockup. The actions stay live the whole way.

Set it on an invented business called Sampleton, with its own drawn or generated pictures and no one else's files. It suits: Property, hospitality, architecture: any subject with a strong shape of its own to borrow. Do not let it fail the way this kind of piece usually does: Locking the scroll or covering the actions while the curtain plays. The exemplar did both, for about ten seconds.

It must work with the keyboard, on a phone, with reduced motion respected and no text under 12px. Tell me which libraries you chose and why.