The diary

Diary: your ink sinks into the page and it writes back. Study: everything stays; it annotates alongside. Quiz: it tests you on the page.
Ink: the reply resolves out of a blot, through a wrong mark, into the word. Taught hand: replayed as pen strokes from the characters you taught it.
Caveat carries across a room. Homemade Apple looks more like real handwriting, close up.
No hand taught yet — replies use a font. Teach ~70 characters (5 minutes) and it writes in real pen strokes.
Swipe left from the right-hand edge, or tap the page number, to turn the page. Each page keeps its own ink; the conversation carries across. Turn off on a tablet so your palm doesn't draw. Off by default. On, replies simply appear, ink and pages stop fading. Leave as-is inside claude.ai. On your own hosting, point this at your Cloudflare Worker (see worker.js) and leave the key blank.