riddle — the diary of Tom Riddle, for the reMarkable Paper Pro
Write on the page with your pen. After a pause, the diary drinks your ink —
your words fade into the paper — the page thinks for a moment, and an answer
writes itself back in a flowing hand, stroke by stroke, then fades away.
No screen glow, no keyboard, no chat UI. Just ink appearing on paper.
This is the diary from the demo.
🪄 New to this? Start here
You need a reMarkable Paper Pro in developer mode with a launcher installed.
If that sounds like a lot, it isn't — remagic
walks you through turning on developer mode and sets up everything with one
command. Come back here, drop riddle in, and start writing to Tom.
Already have xovi + AppLoad? Install from the remagic
catalog, grab the prebuilt bundle, or
build from source.
Install with remagic (easiest)
Then in AppLoad: tap Reload, then The Diary. Write, and rest your
pen. (Or install it from the Store app right on the tablet.)
Install the prebuilt bundle
Grab riddle-<version>.zip from the latest release
and unzip it into a folder: unzip riddle-*.zip -d riddle
Copy the folder to your tablet:
scp -O -r riddle root@10.11.99.1:/home/root/xovi/exthome/appload/
Add an API key: cp oracle.env.example oracle.env in that folder and put your RIDDLE_OPENAI_KEY in it (any OpenAI-compatible key). Or skip it to use pi.
In AppLoad: tap Reload, then The Diary. Write, and rest your pen.
⚠️ This modifies your device. It runs as root, stops the vendor UI
(in takeover mode), and drives the e-ink engine directly. It has only been
tested on a reMarkable Paper Pro (ferrari, aarch64, OS 3.26–3.27). It may
not work on other models or OS versions, and you use it entirely at your own
risk. Not affiliated with reMarkable AS. Keep SSH access working before you
install anything — that is your escape hatch.
How it works
riddle/ — the app (Rust). Pen input, ink surface, handwriting
synthesis (rasterize → Zhang-Suen thinning → stroke tracing → animated
replay), the oracle process manager, and both display backends.
quill/ — the takeover display host (C/C++). An
epfb-re-style QImage-constructor
interposition shim over the vendor libqsgepaper.so waveform engine,
exposed as a small C ABI (quill_init / quill_buffer / quill_swap)
that riddle links against with --features takeover. Also carries a small
family of demos (scribble, a pen-to-glass latency test, plus map, image,
and GIF renderers).
Gestures
The oracle (the "spirit" in the diary)
The diary's replies come from a vision LLM that reads your handwriting from the
committed page (sent as an inline PNG). There are two backends, chosen at
startup — pick whichever you have:
Option A — any OpenAI-compatible API (easiest, zero setup)
Set an API key and riddle talks straight to an OpenAI-compatible
/chat/completions endpoint. Works with OpenAI, OpenRouter, Groq, a local
server — anything that speaks the format. No extra software on the tablet.
Any vision-capable model works. On the tablet these live in oracle.env
next to the binary (see oracle.env.example, or just run
remagic config riddle — it has one-tap presets for OpenAI, OpenRouter,
and Gemini). Example with OpenRouter:
Two gotchas with thinking models (Gemini 3.x, o-series): set
RIDDLE_OPENAI_REASONING=low for faster first ink (some providers reject
the field on non-thinking models — leave it unset there), and keep
RIDDLE_OPENAI_MAX_TOKENS roomy — hidden reasoning tokens count against it,
and a tight cap starves the visible reply.
Verify your setup before launching the diary:
Measured ~0.9–1.1 s to first ink on-device. The HTTPS is built into riddle
(pure-Rust, no extra libraries).
Option B — pi (the power path)
If you already run pi, riddle will use
a resident pi --mode rpc process kept warm (Node + your subscription auth
loaded once), so each turn pays only model latency. Used automatically when
RIDDLE_OPENAI_KEY is not set.
Both stream the reply sentence-by-sentence, so the quill starts writing seconds
before the model finishes. The persona prompt lives in riddle/src/oracle.rs.
Building
Cross-compiled from x86_64. Two flavours:
Windowed (AppLoad/qtfb) — easiest
Requires xovi + AppLoad on the device.
Install to /home/root/xovi/exthome/appload/riddle/ with
external.manifest.json, appload-launch.sh, and the binary.
Takeover (instant ink) — the one from the demo
Requires the reMarkable SDK toolchain (~/rm-sdk-3.26) because the linked
vendor Qt libs need its glibc, and libqsgepaper.so pulled from your own
device (it is proprietary and not distributed here):
The staged dist/riddle/ is self-contained (binary, libquill.so, launch
scripts, manifest) — copy it to
/home/root/xovi/exthome/appload/riddle/, or publish it to the catalog with
remagic publish dist/riddle. Launching via AppLoad (appload-launch.sh)
detaches into a transient systemd unit, stops xochitl, runs the diary, and
always restores xochitl on exit — exit with the power button, a 5-finger
tap, or SIGTERM. If anything wedges:
ssh root@10.11.99.1 'systemctl start xochitl'.
Fonts
The reply hand is Dancing Script
(SIL OFL 1.1 — see riddle/fonts/OFL.txt).
License
MIT for everything in this repository (see LICENSE). The vendor libraries it
interposes (libqsgepaper.so, Qt) are not included and must come from
your own device/SDK.