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.

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.

remagic install riddle # checksum-verified download → AppLoad

remagic config riddle # settings form in your browser (+ QR for phone)

Then in AppLoad: tap Reload, then The Diary. Write, and rest your pen. (Or install it from the Store app right on the tablet.)

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 yourRIDDLE_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.

pen (raw evdev, full 4096-level pressure, hardware event rate)

│ strokes

▼

riddle ── idle 2.8s → commit page → PNG ──► oracle (resident LLM process,

│ streams reply sentence-by-sentence)

▼ strokes (Dancing Script → skeletonized to single-pixel pen paths)

display backend

├── qtfb — windowed, inside xochitl (AppLoad app)

└── quill — full takeover: xochitl stopped, vendor e-ink engine

driven directly for instant ink (lowest latency there is)

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 vendorlibqsgepaper.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).

| Do this | And |

|---|---|

| Write, then rest the pen | The diary drinks your ink and Tom replies |

| Flip the marker | Erase |

| Draw a large ? | Summon the built-in guide |

| Tap five fingers at once | Leave the diary |

| Power button | The page turns to "The diary sleeps.", then the tablet suspends; press again to wake exactly where you were |

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:

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.

export RIDDLE_OPENAI_KEY="sk-..." # required

export RIDDLE_OPENAI_BASE="https://api.openai.com/v1" # optional (default)

export RIDDLE_OPENAI_MODEL="gpt-4o-mini" # optional; must see images

export RIDDLE_OPENAI_REASONING="low" # thinking models only

export RIDDLE_OPENAI_MAX_TOKENS="2000" # runaway guard

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:

export RIDDLE_OPENAI_KEY="$OPENROUTER_API_KEY"

export RIDDLE_OPENAI_BASE="https://openrouter.ai/api/v1"

export RIDDLE_OPENAI_MODEL="openai/gpt-4o-mini"

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:

riddle --oracle-test path/to/handwriting.png # prints the streamed reply

Measured ~0.9–1.1 s to first ink on-device. The HTTPS is built into riddle (pure-Rust, no extra libraries).

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

Cross-compiled from x86_64. Two flavours:

Requires xovi + AppLoad on the device.

cd riddle

cargo build --release --target aarch64-unknown-linux-gnu

Install to /home/root/xovi/exthome/appload/riddle/

with

external.manifest.json

, appload-launch.sh

, and the binary.

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):

cd quill && ./build.sh # pulls libqsgepaper.so from the device over

ssh, builds libquill.so + the demos

cd ../riddle && ./build-takeover.sh

./scripts/make-bundle.sh # stages the AppLoad bundle in dist/riddle/

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'

The reply hand is Dancing Script

(SIL OFL 1.1 — see riddle/fonts/OFL.txt

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.